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Global warming, changes in the hydrological cycle and enhanced marine primary productivity all have been invoked as having contributed to the occurrence of widespread ocean anoxia during the Cenomanian–Turonian oceanic anoxic event (OAE2; ~94 Ma), but disentangling these factors on a regional scale has remained problematic. In an attempt to separate these forcing factors, we generated palynological and organic geochemical records using a core spanning the OAE2 from Wunstorf, Lower Saxony Basin (LSB; northern Germany), which exhibits cyclic black shale–marl alternations related to the orbital precession cycle.
Despite the widely varying depositional conditions complicating the interpretation of the obtained records, TEX86H indicates that sea-surface temperature (SST) evolution in the LSB during OAE2 resembles that of previously studied sites throughout the proto-North Atlantic. Cooling during the so-called Plenus Cold Event interrupted black shale deposition during the early stages of OAE2. However, TEX86 does not vary significantly across black shale–marl alternations, suggesting that temperature variations did not force the formation of the cyclic black shale horizons. Relative (i.e., with respect to marine palynomorphs) and absolute abundances of pollen and spores are elevated during phases of black shale deposition, indicative of enhanced precipitation and run-off. High abundances of cysts from inferred heterotrophic and euryhaline dinoflagellates supports high run-off, which likely introduced additional nutrients to the epicontinental shelf resulting in elevated marine primary productivity.
We conclude that orbitally forced enhanced precipitation and run-off, in tandem with elevated marine primary productivity, were critical in cyclic black shale formation on the northern European epicontinental shelf and potentially for other OAE2 sections in the proto-Atlantic and Western Interior Seaway at similar latitudes as well.
Enhanced aridification of Central Asia driven by the combined effects of orogenic surface uplift, Paratethys retreat, changes in atmospheric moisture transport and global cooling is one of the most prominent Cenozoic climate change events of the Northern Hemisphere. Deciphering regional long-term patterns of Central Asian hydrology is, therefore, a key element in understanding the role of Northern Hemisphere mid-latitude drying in the global hydrological system. Pedogenic carbonates record information of the paleoecosystem, the paleogeography, hydrology, tectonic and climatic conditions as well as the sedimentary regime during the time in which they formed. The calcrete-bearing paleosols in continental sedimentary basins yield the possibility for understanding these processes, mechanisms and controlling factors. This study characterizes long-term paleoenvironmental conditions between the late Oligocene and early Miocene in SE Kazakhstan based on stable isotopes, elemental geochemistry and laser ablation U-Pb geochronology from alluvial, fluvial and pedogenic deposits. The main topics addressed in this thesis are paleosol and calcrete formation processes in the light of geochemistry, tectonic and climatic influences on both, as well as the paleoenvironmental and hydrological conditions which led to these processes.
The sedimentological succession of the 14 km-long Kendyrlisai Valley in the Ili Basin, SE Kazakhstan in Central Asia, yields exceptional well-developed paleosols which provide an insight into the relationship between tectonics and sedimentation as well as soil formation processes. The valley accommodates more than 600 m of siliciclastic sediments deposited in a fluvial to alluvial environment in the lower part which grade into lacustrine to fluvial deposition with minor gypsum accumulation in the upper part. The yet undated sediments of Kendyrlisai Valley are compared with a biostratigraphically dated and well described succession in an adjacent location. The correlation of the two successions revealed a proximal-distal relation with the Kendyrlisai Valley succession represents the basin margin position with coarse alluvial-fluvial sediments. The calcrete nodules in Kendyrlisai Valley paleosols give the opportunity of U-Pb dating with LA-ICP-MS which uses the variation in both U and Pb to directly date the calcite. The U-Pb dating revealed a late Oligocene-early Miocene age for the investigated section. The analysis of facies and geochemistry of the paleosol profiles in Kendyrlisai Valley gives insight into calcretization stages, pedogenic processes and landscape stability. Kendyrlisai Valley paleosols show a low to moderate weathering intensity with the highest weathering intensity between 0.5 and 0.8 m depth in the paleosol profile. The comparison between acid leachable and non-acid leachable fraction indicate an incorporation of Ca and Ba in incipient calcrete calcite, whereas clay minerals adsorb Mg and Sr. During the evolution from early to more mature calcrete stages, i.e. calcrete nodules, Ba is lost by dissolution and subsequently adsorbed on clay minerals. The nodules consist almost exclusively of pure calcium carbonate with rare substitution of Ca by Mg indicating a constant supply of Ca by weathering and solution during calcrete formation. The occurrence of Mg-bearing clay minerals indicates high evaporative conditions with alkaline waters (pH >9).
Sampled calcrete nodule cross sections reveal more than one weathering and calcrete formation phase with a higher supply of Ca, Mg and Fe during early phases. The organic and inorganic carbon isotope composition of the calcrete nodules reflects C3 metabolism under occasionally moisture stress, resulting in higher δ13C values and lower respiration rates. This study also presents calculated atmospheric pCO2 values from the calcrete nodules with the equation from Cerling et al. (1999). The average calculated CO2 concentration for Kendyrlisai Valley paleosols is 313 ± 110 ppmv. The comparison with data from other studies during the late Oligocene–early Miocene reveal lower values for Kendyrlisai Valley paleosols, which may stem from an underestimation of the plant-respired CO2.
The knowledge of the variability within the paleosols and calcrete nodules enables a reliable paleoclimatic interpretation for the Kendyrlisai Valley and beyond the Ili Basin. Sedimentary facies and geochemical weathering indices suggest an increased surface and groundwater discharge fed by orographically-enhanced precipitation in the Tien Shan hinterland. In contrast, pedogenic stable isotope data and elevated rates of Mg fixation in clay minerals mirror enhanced rates of evaporation in the vadose zone due to protracted aridification. This study posits that pronounced surface uplift of the Tien Shan Mountains during the Oligocene–Miocene transition promoted regionally increased orographic precipitation and the development of fluvial discharge systems.
The comparison with other studies in adjacent basins creates a precipitation pattern for Central Asia during the late Oligocene to early Miocene. The westerlies supplied Central Asia with atmospheric moisture from the West, possibly from the Eastern Paratethys. The uplifting Tien Shan Mountain ranges captured this moisture on their luv-side, resulting in a pronounced orographic rainfall in the adjacent Ili and Issyk Kul Basins. The Tarim Basin and the Valley of Lakes experienced drier conditions due to the rain shadow effect on the lee-side of the Tien Shan and Altai Mountains. In course of this findings, the thesis highlights the crucial role the Tien Shan Mountains play and had been playing in former times as an orographic barrier for the distribution of atmospheric moisture across Central Asia.
Für 103 langperiodisch Veränderliche werden B-R, im wesentlichen aus
AAVSO-Material, in Diagrammen dargestellt. Ein Zusammenhang zwischen Form der lichtkurve und Entwicklung der B-R besteht offenbar nicht. Möglicherweise sind geringe Streuung und ausgeprägte Zickzackform der B-R Indikatoren sprunghafter Periodenänderungen.
Knowledge about mass discrimination effects in a chemical ionization mass spectrometer (CIMS) is crucial for quantifying, e.g., the recently discovered extremely low volatile organic compounds (ELVOCs) and other compounds for which no calibration standard exists so far. Here, we present a simple way of estimating mass discrimination effects of a nitrate-based chemical ionization atmospheric pressure interface time-of-flight (CI-APi-TOF) mass spectrometer. Characterization of the mass discrimination is achieved by adding different perfluorinated acids to the mass spectrometer in amounts sufficient to deplete the primary ions significantly. The relative transmission efficiency can then be determined by comparing the decrease of signals from the primary ions and the increase of signals from the perfluorinated acids at higher masses. This method is in use already for PTR-MS; however, its application to a CI-APi-TOF brings additional difficulties, namely clustering and fragmentation of the measured compounds, which can be treated with statistical analysis of the measured data, leading to self-consistent results. We also compare this method to a transmission estimation obtained with a setup using an electrospray ion source, a high-resolution differential mobility analyzer and an electrometer, which estimates the transmission of the instrument without the CI source. Both methods give different transmission curves, indicating non-negligible mass discrimination effects of the CI source. The absolute transmission of the instrument without the CI source was estimated with the HR-DMA method to plateau between the m∕z range of 127 and 568 Th at around 1.5 %; however, for the CI source included, the depletion method showed a steady increase in relative transmission efficiency from the m∕z range of the primary ion (mainly at 62 Th) to around 550 Th by a factor of around 5. The main advantages of the depletion method are that the instrument is used in the same operation mode as during standard measurements and no knowledge of the absolute amount of the measured substance is necessary, which results in a simple setup.
Knowledge about mass discrimination effects in a chemical ionization mass spectrometer (CIMS) is crucial for quantifying, e.g., the recently discovered extremely low volatile organic compounds (ELVOCs) and other compounds for which no calibration standard exists so far. Here, we present a simple way of estimating mass discrimination effects of a nitrate-based chemical ionization atmospheric pressure interface time-of-flight (CI-APi-TOF) mass spectrometer. Characterization of the mass discrimination is achieved by adding different perfluorinated acids to the mass spectrometer in amounts sufficient to deplete the primary ions significantly. The relative transmission efficiency can then be determined by comparing the decrease of signals from the primary ions and the increase of signals from the perfluorinated acids at higher masses. This method is in use already for PTR-MS; however, its application to a CI-APi-TOF brings additional difficulties, namely clustering and fragmentation of the measured compounds, which can be treated with statistical analysis of the measured data, leading to selfconsistent results. We also compare this method to a transmission estimation obtained with a setup using an electrospray ion source, a high-resolution differential mobility analyzer and an electrometer, which estimates the transmission of the instrument without the CI source. Both methods give different transmission curves, indicating non-negligible mass discrimination effects of the CI source. The absolute transmission of the instrument without the CI source was estimated with the HR-DMA method to plateau between the m=z range of 127 and 568 Th at around 1.5 %; however, for the CI source included, the depletion method showed a steady increase in relative transmission efficiency from the m=z range of the primary ion (mainly at 62 Th) to around 550 Th by a factor of around 5. The main advantages of the depletion method are that the instrument is used in the same operation mode as during standard measurements and no knowledge of the absolute amount of the measured substance is necessary, which results in a simple setup.
This paper compares measurements of gaseous and particulate emissions from a wide range of biomass-burning plumes intercepted by the NASA DC-8 research aircraft during the three phases of the ARCTAS-2008 experiment: ARCTAS-A, based out of Fairbanks, Alaska USA (3 April to 19 April 2008); ARCTAS-B based out of Cold Lake, Alberta, Canada (29 June to 13 July 2008); and ARCTAS-CARB, based out of Palmdale, California, USA (18 June to 24 June 2008). Extensive investigations of boreal fire plume evolution were undertaken during ARCTAS-B, where four distinct fire plumes that were intercepted by the aircraft over a range of down-wind distances (0.1 to 16 hr transport times) were studied in detail. Based on these analyses, there was no evidence for ozone production and a box model simulation of the data confirmed that net ozone production was slow (on average 1 ppbv h−1 in the first 3 h and much lower afterwards) due to limited NOx. Peroxyacetyl nitrate concentrations (PAN) increased with plume age and the box model estimated an average production rate of ~80 pptv h−1 in the first 3 h. Like ozone, there was also no evidence for net secondary inorganic or organic aerosol formation. There was no apparent increase in aerosol mass concentrations in the boreal fire plumes due to secondary organic aerosol (SOA) formation; however, there were indications of chemical processing of the organic aerosols. In addition to the detailed studies of boreal fire plume evolution, about 500 smoke plumes intercepted by the NASA DC-8 aircraft were segregated by fire source region. The normalized excess mixing ratios (i.e. ΔX/ΔCO) of gaseous (carbon dioxide, acetonitrile, hydrogen cyanide, toluene, benzene, methane, oxides of nitrogen (NOx), ozone, PAN) and fine aerosol particulate components (nitrate, sulfate, ammonium, chloride, organic aerosols and water soluble organic carbon) of these plumes were compared.
This paper compares measurements of gaseous and particulate emissions from a wide range of biomass-burning plumes intercepted by the NASA DC-8 research aircraft during the three phases of the ARCTAS-2008 experiment: ARCTAS-A, based out of Fairbanks, Alaska, USA (3 April to 19 April 2008); ARCTAS-B based out of Cold Lake, Alberta, Canada (29 June to 13 July 2008); and ARCTAS-CARB, based out of Palmdale, California, USA (18 June to 24 June 2008). Approximately 500 smoke plumes from biomass burning emissions that varied in age from minutes to days were segregated by fire source region and urban emission influences. The normalized excess mixing ratios (NEMR) of gaseous (carbon dioxide, acetonitrile, hydrogen cyanide, toluene, benzene, methane, oxides of nitrogen and ozone) and fine aerosol particulate components (nitrate, sulfate, ammonium, chloride, organic aerosols and water soluble organic carbon) of these plumes were compared. A detailed statistical analysis of the different plume categories for different gaseous and aerosol species is presented in this paper.
The comparison of NEMR values showed that CH4 concentrations were higher in air-masses that were influenced by urban emissions. Fresh biomass burning plumes mixed with urban emissions showed a higher degree of oxidative processing in comparison with fresh biomass burning only plumes. This was evident in higher concentrations of inorganic aerosol components such as sulfate, nitrate and ammonium, but not reflected in the organic components. Lower NOx NEMRs combined with high sulfate, nitrate and ammonium NEMRs in aerosols of plumes subject to long-range transport, when comparing all plume categories, provided evidence of advanced processing of these plumes.
Many natural minerals exist in the form of a solid solution. The systematic changes in structural and physical properties of oxide solid solutions are of geological importance and allow for wide applications. In order to understand the composition-structureproperty relations, substitutional solid solutions of CuxZn2−xTiO4, ZnxMg1−xTi2O5 and CuxMg1−xTi2O5 have been synthesised by mechanochemical activation assisted solid state synthesis. Self-propagating high-temperature synthesis has been employed to achieve the interstitial solid solutions of Ti5Si3Zx (Z refers to the element boron or oxygen).
The changes in the crystal structure and physical properties due to the formation of solid solutions are investigated by employing X-ray diffraction, neutron diffraction, Raman spectroscopy, low-temperature heat capacity, thermal expansion, scanning electron microscopy, UV-vis spectroscopy, plane-wave ultrasound spectroscopy and density functional theory calculations.
A comprehensive study of sillenite Bi12SiO20 single-crystal properties, including elastic stiffness and piezoelectric coefficients, dielectric permittivity, thermal expansion and molar heat capacity, is presented. Brillouin-interferometry measurements (up to 27 GPa), which were performed at high pressures for the first time, and ab initio calculations based on density functional theory (up to 50 GPa) show the stability of the sillenite structure in the investigated pressure range, in agreement with previous studies. Elastic stiffness coefficients c11 and c12 are found to increase continuously with pressure while c44 increases slightly for lower pressures and remains nearly constant above 15 GPa. Heat-capacity measurements were performed with a quasi-adiabatic calorimeter employing the relaxation method between 2 K and 395 K. No phase transition could be observed in this temperature interval. Standard molar entropy, enthalpy change and Debye temperature are extracted from the data. The results are found to be roughly half of the previous values reported in the literature. The discrepancy is attributed to the overestimation of the Debye temperature which was extracted from high-temperature data. Additionally, Debye temperatures obtained from mean sound velocities derived by Voigt-Reuss averaging are in agreement with our heat-capacity results. Finally, a complete set of electromechanical coefficients was deduced from the application of resonant ultrasound spectroscopy between 103 K and 733 K. No discontinuities in the temperature dependence of the coefficients are observed. High-temperature (up to 1100 K) resonant ultrasound spectra recorded for Bi12MO20 crystals revealed strong and reversible acoustic dissipation effects at 870 K, 960 K and 550 K for M = Si, Ge and Ti, respectively. Resonances with small contributions from the elastic shear stiffness c44 and the piezoelectric stress coefficient e123 are almost unaffected by this dissipation.
Deriving stratospheric age of air spectra using an idealized set of chemically active trace gases
(2019)
Analysis of stratospheric transport from an observational point of view is frequently realized by evaluation of the mean age of air values from long-lived trace gases. However, this provides more insight into general transport strength and less into its mechanism. Deriving complete transit time distributions (age spectra) is desirable, but their deduction from direct measurements is difficult. It is so far primarily based on model work. This paper introduces a modified version of an inverse method to infer age spectra from mixing ratios of short-lived trace gases and investigates its basic principle in an idealized model simulation. For a full description of transport seasonality the method includes an imposed seasonal cycle to gain multimodal spectra. An ECHAM/MESSy Atmospheric Chemistry (EMAC) model simulation is utilized for a general proof of concept of the method and features an idealized dataset of 40 radioactive trace gases with different chemical lifetimes as well as 40 chemically inert pulsed trace gases to calculate pulse age spectra. It is assessed whether the modified inverse method in combination with the seasonal cycle can provide matching age spectra when chemistry is well-known. Annual and seasonal mean inverse spectra are compared to pulse spectra including first and second moments as well as the ratio between them to assess the performance on these timescales. Results indicate that the modified inverse age spectra match the annual and seasonal pulse age spectra well on global scale beyond 1.5 years of mean age of air. The imposed seasonal cycle emerges as a reliable tool to include transport seasonality in the age spectra. Below 1.5 years of mean age of air, tropospheric influence intensifies and breaks the assumption of single entry through the tropical tropopause, leading to inaccurate spectra, in particular in the Northern Hemisphere. The imposed seasonal cycle wrongly prescribes seasonal entry in this lower region and does not lead to a better agreement between inverse and pulse age spectra without further improvement. Tests with a focus on future application to observational data imply that subsets of trace gases with 5 to 10 species are sufficient for deriving well-matching age spectra. These subsets can also compensate for an average uncertainty of up to ±20 % in the knowledge of chemical lifetime if a deviation of circa ±10 % in modal age and amplitude of the resulting spectra is tolerated.
Analysis of stratospheric transport from an observational point of view is frequently realized by evaluation of mean age of air values from long-lived trace gases. However, this provides more insight into general transport strength and less into its mechanism. Deriving complete transit time distributions (age spectra) is desirable, but their deduction from direct measurements is difficult and so far primarily achieved by assumptions about dynamics and spectra themselves. This paper introduces a modified version of an inverse method to infer age spectra from mixing ratios of short-lived trace gases. For a full description of transport seasonality the formulation includes an imposed seasonal cycle to gain multimodal spectra. The EMAC model simulation used for a proof of concept features an idealized dataset of 40 radioactive trace gases with different chemical lifetimes as well as 40 chemically inert pulsed trace gases to calculate pulse age spectra. Annual and seasonal mean inverse spectra are compared to pulse spectra including first and second moments as well as the ratio between them to assess the performance on these time scales. Results indicate that the modified inverse age spectra match the annual and seasonal pulse age spectra well on global scale beyond 1.5 years mean age of air. The imposed seasonal cycle emerges as a reliable tool to include transport seasonality in the age spectra. Below 1.5 years mean age of air, tropospheric influence intensifies and breaks the assumption of single entry through the tropical tropopause, leading to inaccurate spectra in particular in the northern hemisphere. The imposed seasonal cycle wrongly prescribes seasonal entry in this lower region and does not lead to a better agreement between inverse and pulse age spectra without further improvement. As the inverse method aims for future implementation on in situ observational data, possible critical factors for this purpose are delineated finally.
Das Ziel dieser Arbeit ist die Untersuchung der stratosphärischen Meridionalzirkulation mit Hilfe von chemisch aktiven Spurengasen. Diese motiviert sich durch die Tatsache, dass der Klimawandel neben den viel erforschten Auswirkungen auf die Troposphäre, auch Reaktionen in der Stratosphäre zur Folge hat, welche bisher weit weniger tiefgehend untersucht wurden. Das macht die Stratosphäre zu einem aktuellen und frequentierten Forschungsgebiet der experimentellen und theoretischen Meteorologie. Neben vereinzelten hochaufgelösten in-situ Messungen und globalen Satellitendaten sind es hier vor allem globale numerische Klima-Chemiemodelle, die für Analysen genutzt werden. Für diese Arbeit wurden Daten des EMAC-Modells (engl.: ECHAM/MESSy Atmospheric Chemistry) ausgwertet, welche im Rahmen der ESCiMo (engl.: Earth System Chemistry integrated Modelling) Initiative vom MESSy-Konsortium (engl.: Modular Earth Submodel System) erstellt wurden. Die Zielsetzung dieser Arbeit war, ob sich etwaige Änderungen des stratosphärischen Transports anhand von modellierten, chemisch aktiven, idealisierten Spurengasen feststellen lassen. Idealisiert bedeutet hierbei, dass diese Gase ein konstantes Mischungsverhältnis am Erdboden aufweisen und den identischen chemischen Prozessen unterliegen wie die realistischen Tracer. Dies hat zur Folge, dass diese Spurengase somit nicht in das Strahlungsbudget des Modells rückkoppeln und ihre Verteilung nicht durch zeitliche troposphärische Trends beeinflusst wird. Zur Analyse des stratosphärischen Transports wurden die Differenzen der monatlich gemittelten Mischungsverhältnisse zweier Zeitpunkte der verschiedenen Substanzen im Vertikalprofil betrachtet und ausgewertet, wobei hier die photolytische Lebenszeit und die Zeitskala des Transports zu berücksichtigen war. Um die Saisonalität von Transport und Chemie zu berücksichtigen, wurden dazu die Monate März, Juni, September und Dezember analysiert.
Die Resultate zeigten, dass chemisch aktive Substanzen in der Tat geeignet sind Änderungen in der Dynamik festzustellen. So stellte sich heraus, dass mit einer allgemeinen Intensivierung der stratosphärischen Meridionalzirkulation im kommenden Jahrhundert gerechnet werden kann, wobei hiervon besonders die untere Stratosphäre betroffen ist. Eine Differenzierung welche Komponente der Zirkulation (Residualtransport oder bidirektionale quasi-horizontale Mischung) hierbei von übergeordneter Bedeutung ist, konnte nicht spezifiziert werden. Um abzuschätzen, ob sich die Änderung der Zirkulation durch Änderungen in den Mischungsverhältnissen von chemisch aktiven Substanzen mit Hilfe von direkten Messungen nachweisen lässt, wurde die atmosphärische Variabilität des Modells bestimmt und mit den Veränderungen dieser Mischungsverhältnisse verglichen. Es zeigte sich, dass diese modellierte atmosphärische Variabilität zum Teil deutlich größer war, als die Differenzen der Mischungsverhältnisse und so ohne eine Vielzahl von in-situ Messungen keine eindeutige Aussage zulassen. Um eine statistisch valide Aussage treffen zu können, müssen daher mehrere Messreihen innerhalb eines Monats durchgeführt werden. Zudem stellte sich heraus, dass der Monat Juni der bestmögliche Messzeitraum ist, da hier die natürliche Variabilität am geringsten ist. Zuletzt wurden die Spurengase mit vergleichsweise kleiner chemischer Lebenszeit auf normierten N2O-Isoplethen untersucht und die Verschiebung dieser Kurve zwischen den zwei Zeitpunkten analysiert. Die so gewonnenen Resultate ließen den Schluss zu, dass sich auf diese Weise die atmosphärische Variabilität reduzieren lässt und bei Nutzung mit experimentellen Daten eine zu den Tracer-Differenzen konsistente Aussage zulässt. So bestärkte diese Methode die These, dass sich der stratosphärische Transport innerhalb des 21. Jahrhunderts wahrscheinlich verstärken wird.
Sedimentary charcoal records are widely used to reconstruct regional changes in fire regimes through time in the geological past. Existing global compilations are not geographically comprehensive and do not provide consistent metadata for all sites. Furthermore, the age models provided for these records are not harmonised and many are based on older calibrations of the radiocarbon ages. These issues limit the use of existing compilations for research into past fire regimes. Here, we present an expanded database of charcoal records, accompanied by new age models based on recalibration of radiocarbon ages using IntCal20 and Bayesian age-modelling software. We document the structure and contents of the database, the construction of the age models, and the quality control measures applied. We also record the expansion of geographical coverage relative to previous charcoal compilations and the expansion of metadata that can be used to inform analyses. This first version of the Reading Palaeofire Database contains 1676 records (entities) from 1480 sites worldwide. The database (RPDv1b – Harrison et al., 2021) is available at https://doi.org/10.17864/1947.000345.
Auf dem Piesberg bei Osnabrück konnten Gletscherschrammen beobachtet werden. Sie verlaufen überwiegend von NNE nach SSW. Diese Richtung stimmt gut mit Einregelungsmessungen an Geschiebe-Längsachsen in dem die Schrammenfläche bedeckenden Geschiebelehm überein. Gletscherschrammen und Geschiebelehm haben saalezeitliches Alter (Drenthe-Stadium).
An der Basis einer Brekzie aus zechsteinzeitlichen Karbonatgesteinen konnten auf dem Hüggel-Horst Sedimente mit mariner Fauna (Ober-Miozän: Langenfelde-Gram) beobachtet werden. Ihre Fossilführung und Petrographie wird beschrieben. Sie sind in Höhlen, die bei Subrosion von Zechstein-Sulfaten entstanden, im küstennahen Bereich des Miozän-Meeres eingespült und abgelagert worden. Sie belegen, daß der Hüggel-Horst schon im Miozän gehoben und bis auf die Zechstein-Gesteine abgetragen worden war.
Ziel der vorliegenden Arbeit ist es, neben einer Gliederung der Zechstein-Serien im Bereich des Hüggels die Genese der allochthonen Schollen (Silberberg-Großheide-Scholie und Heidberg-Jägerberg-Scholle) in seinem südlichen Vorland zu diskutieren. Die Zechstein-Gesteine liegen in dolomitischer Randfazies vor, die eine geilauere Untergliederung z. Zt, nur bedingt zuläßt. Vermutlich sind während des Werra- und Staßfurt-Zyklus Sulfate (A 1 - A 2) ausgefällt worden, die eine mächtige Anhydrit-Gesteinseinschaltung innerhalb der Zechstein-Serien bildeten. Hinweise auf nennenswerte salinare Bildungen im Bereich des Hüggels gibt es nicht. Die bislang für die Genese der allochthonen Schollen im südlichen Hüggel-Vorland erarbeiteten Modelle (NIENHAUS 1953; LATZE 1953; KELLER 1974) können nicht bestätigt werden. Stattdessen wird versucht, die Bildung der Schollen durch Schub- oder Gleitdeckentektonik zu erklären. Es wird angenommen, daß die Silberberg-Großheide-Scholie aus dem Dachbereich des Hüggel- Horstes stammt. Schubdecken-Modell: Die Heidberg-Jägerberg-Scholle und Kreide-Gesteine in Dolinen nördlich des Hüggels sind Reste einer Schubdecke, die von N kommend beim Übergleiten des Hüggel- Horstes dessen Dach (Silberberg-Großheide-Scholle) in das südliche Hüggel-Vorland schob. Gleitdecken-Modell: Während der Hebung des Hüggel-Horstes kam es an übersteilten Hängen zum gravitativen Abgleiten der beiden Schollen in das südliche Hüggel-Vorland.
Im Rahmen von Flurbereinigungsmaßnahmen wurde bei Glandorf-Averfehrden
(Bad Laer, Landkreis Osnabrück) am NW-Hang des Hülsberges
ein großer Findling freigelegt (TK 25 Nr. 3913 Ostbevern, R: 342955, H:
577384). Er wurde am 2. Oktober 1979 gehoben und ca. 300 m südsüdwestlich
des Fundortes an der B 475 als Naturdenkmal aufgestellt.
In drei Aufschlüssen am Schafberg ist die Basis der Zechstein-Ablagerungen (Oberperm) mit "Zechsteinkonglomerat" und "Kupferschiefer" untersucht worden (Petrographie, Mineralogie, Geochemie). Im Zechsteinkonglomerat ist das Auftreten von windgeschliffenen Geröllen bemerkenswert. Der Kupferschiefer erreicht am W-Rand des Schafbergs mit mehr als 2,5 m eine ungewöhnlich hohe Mächtigkeit. Sein Metallgehalt liegt deutlich über den für "normale" Tonsteine üblichen Werten, erreicht aber keine wirtschaftlich interessanten Konzentrationen. Zechsteinkonglomerat und Kupferschiefer wurden am S-Rand des zechstelnzeitltchen Meeres im Bereich der "Hunte-Schwelle" abgelagert.
Im Wiehengebirge (Osnabrücker Bergland) wurden die lithostratigraphisch gegliederten Gesteinsfolgen des Oberjura (Oxford, Kimmeridge, Gigas-Schichten bis Eimbeckhäuser Platten kalk) in zwei Tagesaufschlüssen am Linken-Berg bei Preußisch Oldendorf und am Osterberg bei Wehrendorf mit einer Gamma-Sonde nach dem Scintillometer-Prinzip vermessen. Oie synthetisch erzeugten Gamma- Kurven lassen sich eindeutig mit den Gamma-ray-Kurven der in der Nähe niedergebrachten Bohrungen vergleichen.
Beim Bau eines Regenrückhaltebeckens am Roten Berg in Hasbergen traten zwei kleine Erdfälle auf. Sie werden auf Karsterscheinungen in lösungsfähigen Gesteinen des Zechsteins zurückgeführt. Zechsteinzeitliche Sulfatgesteine sind in einer Tiefe von etwa 70-100 m unter der Baugrubensohle zu vermuten. Es gibt keine Hinweise auf einen Zusammenhang der Bildung dieser Erdfälle mit dem in der Nähe umgegangenen Bergbau. Auch wenn das Gebiet des Roten Berges außerhalb der ehemaligen Bergbaugebiete nicht sehr erdfallgefährdet erscheint, sollten bei Baumaßnahmen in diesem Gebiet vorsorglich einige technisch-konstruktive Sicherungsmaßnahmen getroffen werden.
Von der Gemeinde Hagen a.T.W. wurde am Butterberg ein ehemaliger Steinbruch im Osning-Sandstein durch die Anlage eines Schurfgrabens so erweitert, daß jetzt die Basis des Osning-Sandsteins und etwa 20, m der Schichtenfolge aus seinem Liegenden freigelegt sind. Die Basis des Osning-Sandsteins besteht aus einem dünnen Geröllhorizont, dem Osning-Konglomerat. Das Konglomerat wurde transgressiv auf Schichten der Bückeberg-Folge 1 (tiefster "Wealden") geschüttet. Unter den Gesteinen der Bückeberg-Folge, die mit einer Restmächtigkeit von nur noch etwa 5 m erhalten sind, treten in dem Schurfgraben noch ca. 15 m Ablagerungen des Serpulits auf. Dieser neu geschaffene Aufschluß wird langfristig - als Naturdenkmal geschützt - erhalten bleiben.
Durch sechs Bohrungen am S-Hang des Silberberges wurde der südliche Rand der "Silberberg-Großheide-Scholle" geologisch untersucht. Die Ergebnisse bestätigen im wesentlichen das von NIENHAUS (1953), LOTZE (1953), KELLER (1974) und HARMS (1981) gegebene Bild über den geologischen Aufbau dieses Gebietes: Die aus Zechstein- und Trias-Gesteinen aufgebaute Silberberg-Großheide-Scholieliegt schlüsselförmigauf einer geschlossenen Unterlage aus Jura-Tonstein.
16 moderne Gesteinsanalysen aus den z. T. eisenerzhaitigen Zechstein-Serien (Mutterflöz, Kupferschiefer und Zechsteinkalk) des Hüggels werden vorgestellt. Sie werden durch ältere Analysen von Gesteinen des "höheren" Zechsteins ("Plattiger- und Massiger- Dolomit") aus dem südlich des Hüggels gelegenen Silberberg-Gebiet ergänzt.
Schon zu früheren Zeiten in der Erdgeschichte gab es Warmzeiten durch starke Treibhauseffekte, mit tropischen Temperaturen in weiten Teilen der Erde, hohem Meeresspiegel und massivem Artensterben. Das belegen Daten aus der Paläoklimatologie. Wenn man heutige Klimamodelle auf solche geologischen Warmzeiten anwendet, kann man sie testen und verbessern. So verhilft die Paläoklimatologie zu einem präziseren Blick in unsere Klimazukunft.
Der Paläontologe und das Meer : Eberhard Gischler erforscht das Klimagedächtnis von Korallenriffen
(2018)
Climatic and biogeographical drivers of functional diversity in the flora of the Canary Islands
(2022)
Aim: Functional traits can help us to elucidate biogeographical and ecological processes driving assemblage structure. We analysed the functional diversity of plant species of different evolutionary origins across an island archipelago, along environmental gradients and across geological age, to assess functional aspects of island biogeographical theory.
Location: Canary Islands, Spain.
Major taxa studied: Spermatophytes.
Time period: Present day.
Methods: We collected data for four traits (plant height, leaf length, flower length and fruit length) associated with resource acquisition, competitive ability, reproduction and dispersal ability of 893 endemic, non-endemic native and alien plant species (c. 43% of the Canary Island flora) from the literature. Linking these traits to species occurrences and composition across a 500 m × 500 m grid, we calculated functional diversity for endemic, non-endemic native and alien assemblages using multidimensional functional hypervolumes and related the resulting patterns to climatic (humidity) and island biogeographical (geographical isolation, topographic complexity and geological age) gradients.
Results: Trait space of endemic and non-endemic native species overlapped considerably, and alien species added novel trait combinations, expanding the overall functional space of the Canary Islands. We found that functional diversity of endemic plant assemblages was highest in geographically isolated and humid grid cells. Functional diversity of non-endemic native assemblages was highest in less isolated and humid grid cells. In contrast, functional diversity of alien assemblages was highest in arid ecosystems. Topographic complexity and geological age had only a subordinate effect on functional diversity across floristic groups.
Main conclusions: We found that endemic and non-endemic native island species possess similar traits, whereas alien species tend to expand functional space in ecosystems where they have been introduced. The spatial distribution of the functional diversity of floristic groups is very distinct across environmental gradients, indicating that species assemblages of different evolutionary origins thrive functionally in dissimilar habitats.
Questions: Both species turnover and intraspecific trait variation can affect plant assemblage dynamics along environmental gradients. Here, we asked how community assemblage patterns in relation to species turnover and intraspecific variation differ between endemic and non-endemic species. We hypothesized that endemic species show lower intraspecific variation than non-endemic species because they tend to have high rates of in situ speciation, whereas non-endemic species are expected to have a larger gene pool and higher phenotypic plasticity.
Location: La Palma, Canary Islands.
Methods: We established 44 sampling sites along a directional gradient of precipitation, heat load, soil nitrogen, phosphorus and pH. Along this gradient, we estimated species abundances and measured three traits (plant height, leaf area and leaf thickness) on perennial endemic and non-endemic plant species. In total, we recorded traits for 1,223 plant individuals of 43 species. Subsequently, we calculated community-weighted mean traits to measure the relative contribution of species turnover, intraspecific variation and their covariation along the analysed gradient.
Results: The contribution of intraspecific variation to total variation was similar in endemic and non-endemic assemblages. For plant height, intraspecific variation explained roughly as much variation as species turnover. For leaf area and leaf thickness, intraspecific variation explained almost no variation. Species turnover effects mainly drove trait responses along the environmental gradient, but intraspecific variation was important for responses in leaf area to precipitation.
Conclusions: Despite their distinct evolutionary history, endemic and non-endemic plant assemblages show similar patterns in species turnover and intraspecific variation. Our results indicate that species turnover is the main component of trait variation in the underlying study system. However, intraspecific variation can increase individual species’ fitness in response to precipitation. Overall, our study challenges the theory that intraspecific trait variation is more important for the establishment of non-endemic species compared with endemic species.
Oceanic islands only comprise a small amount of the Earth’s land area but harbour a disproportionate amount of global biodiversity. This vast diversity is not only reflected in the taxonomic uniqueness of island biota but also in the remarkable evolution of functional traits. Functional traits, i.e. measurable characteristics that strongly influence the fitness of species, determine how a species responds to its environment and can help to gain more insights into the biogeographical, ecological and evolutionary processes that have shaped island biodiversity. However, research in island biogeography has primarily focused on species richness, and knowledge of functional trait patterns on oceanic islands is scarce. Hence, in this dissertation, I have explored how trait-based approaches can increase our understanding of how biodiversity on oceanic islands assembles and how it is driven by the environment. The Canary Islands (Spain) are a particularly suitable model system to investigate patterns and drivers of biodiversity. The archipelago is characterised by a high variation in environmental heterogeneity and inhabits a unique and well-described native flora. Therefore, I have investigated five principal research questions using the flora (Spermatophytes) of the Canary Islands as a study object. First, I have analysed how climate and biogeography shape the assembly of the Canary Islands flora using a novel trait-based approach. Second, the question of whether rare climates link to functional trait distinctiveness in the native Canary Islands flora was addressed. Third, I have examined how intraspecific trait variation is represented in the native flora of oceanic islands focusing on the succulent scrub of La Palma (Canary Islands). Fourth, this dissertation investigated whether scientific floras can be reliable sources for trait data of plants native to oceanic islands. Finally, I have explored how climate change may impact the native Canary Islands flora by analysing possible climate change-induced shifts in plant species distribution and plant traits.
The results of my dissertation expand the understanding of the importance of biogeography and the environment in determining the functional composition of island floras. I have assessed that traits of endemic plant species did not expand the functional trait space of the Canary Islands but were packed with the ones of non-endemic species. This result hints at a trait convergence in endemic species, possibly driven by non-adaptive speciation processes. Moreover, I have evidenced that humidity is a critical driver of functional diversity in native plant assemblages and particularly leads to a high trait convergence in arid environments via environmental filtering. In contrast, alien species have expanded the Canary Islands flora’s functional trait space. I further have shown that in contrast to native species assemblages, alien species assemblages are characterised by an increasing functional diversity with increasing aridity. This contrasting pattern of functional diversity could pose a potential risk to the native flora of the Canary Islands as a low functional diversity is expected to reduce the resilience of species assemblages to the establishment of more functionally diverse alien plant species. However, in this dissertation, I also have revealed that endemic plant species on the Canary Islands show a high intraspecific variation in arid environments, possibly as an adaptation to environmental stress. Intraspecific variation could help endemic plant species have a competitive advantage over alien species and be more resilient to environmental changes. Furthermore, in this dissertation, I have shown that scientific floras and taxonomic monographs could be used to gain information on quantitative functional traits of plants native to oceanic islands. This finding is particularly relevant for advances in trait-based research, as coverage of trait data for oceanic island floras is extremely poor in global trait databases. Hence, for some of the studies included in this dissertation, trait data were retrieved from scientific floras and taxonomic monographs and used to answer novel scientific research questions. Thus, I have used trait data from the literature to analyse the effect of climate change on the range size of plants native to the Canary Islands. Identifying plant species of particular conservation concern is critical on oceanic islands as many island species have limited distributions and small population sizes, and their niche tracking is impeded by insularity. I have revealed that single-island endemic plants gain less and lose more climatically suitable areas than archipelago endemic and non-endemic native plants due to a climate change-induced decrease in precipitation until 2100...
Biomass burning impacts vegetation dynamics, biogeochemical cycling, atmospheric chemistry, and climate, with sometimes deleterious socio-economic impacts. Under future climate projections it is often expected that the risk of wildfires will increase. Our ability to predict the magnitude and geographic pattern of future fire impacts rests on our ability to model fire regimes, either using well-founded empirical relationships or process-based models with good predictive skill. A large variety of models exist today and it is still unclear which type of model or degree of complexity is required to model fire adequately at regional to global scales. This is the central question underpinning the creation of the Fire Model Intercomparison Project - FireMIP, an international project to compare and evaluate existing global fire models against benchmark data sets for present-day and historical conditions. In this paper we summarise the current state-of-the-art in fire regime modelling and model evaluation, and outline what lessons may be learned from FireMIP.
Biomass burning impacts vegetation dynamics, biogeochemical cycling, atmospheric chemistry, and climate, with sometimes deleterious socio-economic impacts. Under future climate projections it is often expected that the risk of wildfires will increase. Our ability to predict the magnitude and geographic pattern of future fire impacts rests on our ability to model fire regimes, using either well-founded empirical relationships or process-based models with good predictive skill. While a large variety of models exist today, it is still unclear which type of model or degree of complexity is required to model fire adequately at regional to global scales. This is the central question underpinning the creation of the Fire Model Intercomparison Project (FireMIP), an international initiative to compare and evaluate existing global fire models against benchmark data sets for present-day and historical conditions. In this paper we review how fires have been represented in fire-enabled dynamic global vegetation models (DGVMs) and give an overview of the current state of the art in fire-regime modelling. We indicate which challenges still remain in global fire modelling and stress the need for a comprehensive model evaluation and outline what lessons may be learned from FireMIP.
In dieser Arbeit wurden zwei Idealkristallsysteme und drei Systeme, die im weitesten Sinne als Domänenkristalle zu bezeichnen sind, mit quantenmechanischen Methoden untersucht, die auf Dichte-Funktional-Theorie basieren. Dabei wurden je nach System unterschiedliche Eigenschaften der jeweiligen Kristalle betrachtet. Zusätzlich wurden die berechneten Domänenkristalle jeweils mit entsprechenden Idealkristallen bezüglich ihrer Stabilität verglichen. Insgesamt konnte gezeigt werden, dass sich die hier verwendeten Rechenmethoden sehr gut zur Untersuchung von Grundzuständen und Strukturen unter hydrostatischem Druck sowie von Bindungseigenschaften eignen. Desweiteren lieferten die Ergebnisse starke Hinweise darauf, dass Kristalle mit Strukturgradienten nur dann existieren können, wenn sie sich vom Idealkristall um sehr geringe Energien unterscheiden, die unter der Fehlergrenze der hier angewendeten Methode (2-3 kJ/Mol) liegen.
An eclogite barometer has profound importance in the study of upper mantle processes and potential application to diamond prospecting. Studies on the partitioning of Li between clinopyroxene (cpx) and garnet (grt) in natural samples have shown that this particular element is very sensitive to changes in pressure and could be calibrated as the barometer demanded for bimineralic eclogites. Experiments were performed from 4 to 13 GPa and 1100 to 1400°C in the CMAS (CaO, MgO, Al2O3, SiO2) system with Li added as Li3PO4 to quantify this pressure dependence into a barometer expressed in the following equation: P= (0.00255*T-lnKd)/0.2351 where P is in GPa, T is in °C and Kd is defined as the partition coefficient of Li (in ppm) between clinopyroxene and garnet. The experimental pressures are reproduced to ± 0.38 GPa (1σ) by this equation. This barometer is strictly applicable only to CMAS. Experiments at 1300°C, 8-12 GPa showed that Henry’s Law is fulfilled for Li partitioning between cpx and grt in the concentration range of approximately 0.01 – 1 wt% Li. Direct application of the equation to experiments in natural systems performed at 1300°C from 4 GPa to 13 GPa consistently overestimates pressures by approximately 2 GPa. Our previous experiments in the system CaO-MgO-Al2O3-SiO2 + Li3PO4 showed that the partitioning of Li between garnet and clinopyroxene is pressure dependent in eclogitic bulk compositions. This supports experimentally the hypothesis of Seitz et al. (2003), based on the analysis of Li in eclogitic xenoliths and inclusions in diamond, that the partitioning of this particular element between clinopyroxene and garnet is very sensitive to changes in pressure and could be calibrated as a barometer for bimineralic eclogites. In order to calibrate this pressure dependence into a barometer, experiments were performed in natural systems using starting materials sourced from a well preserved eclogitic xenolith from the Roberts Victor kimberlite pipe (South Africa) to extrapolate our findings in CMAS to natural systems. Sixteen multianvil experiments were performed from 4-13 GPa and 1100-1500°C. Our findings reinforced the general trend we observed in the CMAS system, that KdLi cpx-grt for Li decreases with increasing P, and that at P ≥ 12 GPa, garnet is able to incorporate more Li than clinopyroxene. Multiple linear regression was applied to our experimental results to create the barometer: P = (0.000963*T – ln KdLi cpx-grt + 1.581) / 0.252 Where P is pressure in GPa, T is temperature in °C and KdLi cpx-grt is defined as the partitioning coefficient of Li obtained by dividing the concentration of Li in cpx by the concentration of Li in garnet. This barometer reproduces the experimental conditions to ± 0.2 GPa. It is applicable to eclogitic xenoliths, to garnet pyroxenites and to peridotitic and eclogitic inclusions in diamond. Application of the barometer to diamond bearing xenoliths results in pressures in the diamond stability field. Clinopyroxene is easily corrupted in xenoliths and also preferentially takes in Li during short lived metasomatic processes. Care must be taken therefore to analyse primary, unaltered clinopyroxene. Our preliminary application to natural samples shows that the barometer can be applied beyond the experimental range to pressures down to 3 GPa. Seventeen eclogitic xenoliths were chosen from a sample set of greater than 200 for their fresh microscopic and macroscopic appearance and were analyzed for Li content in coexisting garnet (grt) and clinopyroxene (cpx). These samples can be subdivided into two groups on the basis of Mg in cpx (cpfu: cations per formula unit, based on 6 oxygens): Group 1 with Mg > 0.75, and Group 2 with Mg < 0.75. Group 1 xenoliths show lower Li contents in both grt and cpx compared to Group 2. The Li barom ter calibrated in Hanrahan et al. (2009b)/Chapter 3 was applied to these samples as well as available literature data to obtain pressures of provenance - Group 2 xenoliths often provide pressures that appear unrealistic for eclogitic xenoliths. In light of observed crystal chemical relations in the natural samples, a new fitting procedure was applied to the experimental data presented in Chapter 3. This new fit appears to be more realistic than the previous fit, although a strong relationship with Mg# remains present, suggesting that Li-barometry is, at present, only applicable to Mg-rich eclogites. Inclusions in diamond, with the exception of eclogitic inclusions of coexisting majorite and cpx, often yield pressures that are inconsistent with the pressures required for diamond formation. Although an interesting observation when comparing all of the data is that inclusions in diamond have significantly higher average Li concentrations compared to xenoliths, which suggests that Li is highly present in the fluids from which diamonds form in the mantle, an observation which was previously made for the deep mantle as a result of high Li in ferropericlase inclusions in diamond (Seitz et al. 2003).
The biomarker record in two different lakes in central Europe, Lake Albano and Lake Constance, is used to reflect environmental changes and lake system response during the Late Glacial and Holocene. Extractable organic compounds in lake sediments, which can be assigned to their biological source (biomarkers) function as fingerprints of past aquatic or land plant organisms. Using gas chromatography coupled with mass spectrometry, 21 different biomarkers (predominantly steroids and triterpenoids) as well as a variety of n-alkanes, nalkanols, and n-alkanoic acids could be identified in the sediment records of Lake Albano and Lake Constance. In the Holocene sediments of Lake Albano, the distribution of biomarkers such as dinosterol (dinoflagellates), isoarborinol, and diplopterol (aquatic organisms) indicate three biomarker zones: The period between 0-3,800 years BP (zone 3) is characterized by high concentrations of these biomarkers and others such as tetrahymanol and diploptene. Conversely, zone 2 (3,800-6,500 years BP) shows very low concentrations of all autochthonous biomarkers. In zone 1 (6,500–11,480 years BP), dinosterol, isoarborinol, and diplopterol range on a relatively high level, whereas diploptene and tetrahymanol display comparatively low concentrations. The results suggest at least two distinct changes in the predominance of primary producers during the Holocene, which are related to changes in the lake system such as lake mixing and water column stratification. This interpretation is consistent with previous investigations of Lake Albano sediments including pigment and hydrogen index data (Ariztegui et al., 1996b; Guilizzoni et al., 2002). Allochthonous biomarkers such as long-chain n-alkanes, amyrenones and friedelin indicate a development from forest to a more open landscape from 6,000 and 5.000 years BP, respectively. After a period of high concentrations during the first half of the Holocene, all biomarkers derived from deciduous trees exhibit relatively low values until around 1,000 years BP. Again, this is consistent with results from previous pollen investigations (Ariztegui et al., 2000). The sediment core from Upper Lake Constance comprises the Late Glacial and Holocene. It was analysed for biomarkers and inorganic tracers in order to compare the biomarker results with other proxy data from the same core. Magnetic susceptibility (MS) was measured to get a high-resolution stratigraphic framework of the core and to obtain further information about changes of the proportions of allochthonous and autochthonous input. Enhanced concentrations and accumulation rates of dinosterol (biomarker for dinoflagellates) and biogenic calcite give evidence of increasing lake productivity at the beginning of the Holocene followed by a decrease in bioproductivity after around 7,000 years BP. Younger Dryas sediments are characterized by low amounts of both dinosterol and biogenic calcite indicating a low productivity. The comparison of the concentrations and accumulation rates of b-sitosterol and stigmastanol with parameters reflecting lake productivity suggests that both steroids in Lake Constance sediments are mainly derived from terrigenous sources. Biomarkers as well as concentrations and accumulation rates of allochthonous inorganic compounds such as titanium, magnesium and strontium indicate a slightly enhanced allochthonous input after 8,500 years BP. Significant increase of erosive matter input from enhanced soil erosion is not observed before 4,000 years BP. This can be attributed to the combined effects of precipitation increase as a result of climatic deterioration and anthropogenic deforestation which is consistent with observations from other lakes in Central Europe. The MS record of Lake Constance confirms these results by tracing the climatically induced shifts of more intense bioproduction (low MS caused by increased calcite deposition) during the ‘climatic optimum’. This is followed by increasing input of terrigenous sediment compounds during colder and wetter periods which lead to higher MS values in the lake sediments. The occurrence of tetrahymanol in Lake Constance sediments questions the unambiguous use of tetrahymanol as an indicator for water column stratification. Anaerobic organic macroaggregates within the oxygenated, photic zone of the water column have to be considered as a possible living space for anaerobic microorganisms containing tetrahymanol. The direct comparison of two very different lakes Albano and Constance with respect to biomarkers indicating climate or environmental change provides a contribution to the recent biomarker research for a better understanding of biomarkers in lacustrine sediments.
Measurements of OH, the sum of peroxy radicals (ROx), non-methane hydrocarbons (NMHCs) and various other trace gases were made at the Meteorological Observatory Hohenpeissenberg in June 2000. The data from an intensive measurement period characterised by high solar insolation (18-21 June) are analysed. The maximum midday OH concentration ranged between 4.5 x 106 molecules cm-3 and 7.4 x 106 molecules cm-3. The maximum total ROx mixing ratio increased from about 55 pptv on 18 June to nearly 70 pptv on 20 and 21 June. A total of 64 NMHCs, including isoprene and monoterpenes, were measured every 1 to 6 hours. The oxidation rate of the NMHCs by OH was calculated and reached a total of over 14 x 106 molecules cm-3 s-1 on two days. A simple photostationary state balance model was used to simulate the ambient OH and ROx concentrations with the measured data as input. The model was able to reproduce the main features of the diurnal profiles of both OH and ROx. The model results proved to be most sensitive to assumptions about the mixing ratio of formaldehyde (HCHO), which was included as a proxy for carbonyl compounds, and about the partitioning between HO2 and RO2. The measured OH concentration and ROx mixing ratios were reproduced well by assuming the presence of 3 ppbv HCHO and a ratio HO2/RO2 between 1:1 and 1:2. The most important source of OH, and conversely the greatest sink for ROx, was the recycling of HO2 radicals to OH. This reaction was responsible for the recycling of more than 45 x 106 molecules cm-3 s-1 on two days. The most important sink for OH, and the largest source of ROx, was the oxidation of NMHCs, in particular, of isoprene and the monoterpenes.
Measurements of OH, total peroxy radicals, non-methane hydrocarbons (NMHCs) and various other trace gases were made at the Meteorological Observatory Hohenpeissenberg in June 2000. The data from an intensive measurement period characterised by high solar insolation (18-21 June) are analysed. The maximum midday OH concentration ranged between 4.5x106 molecules cm-3 and 7.4x106 molecules cm-3. The maximum total ROx (ROx =OH+RO+HO2+RO2) mixing ratio increased from about 55 pptv on 18 June to nearly 70 pptv on 20 and 21 June. A total of 64 NMHCs, including isoprene and monoterpenes, were measured every 1 to 6 hours. The oxidation rate of the NMHCs by OH was calculated and reached a total of over 14x106 molecules cm-3 s-1 on two days. A simple photostationary state balance model was used to simulate the ambient OH and peroxy radical concentrations with the measured data as input. This approach was able to reproduce the main features of the diurnal profiles of both OH and peroxy radicals. The balance equations were used to test the effect of the assumptions made in this model. The results proved to be most sensitive to assumptions about the impact of unmeasured volatile organic compounds (VOC), e.g. formaldehyde (HCHO), and about the partitioning between HO2 and RO2. The measured OH concentration and peroxy radical mixing ratios were reproduced well by assuming the presence of 3 ppbv HCHO as a proxy for oxygenated hydrocarbons, and a HO2/ RO2 ratio between 1:1 and 1:2. The most important source of OH, and conversely the greatest sink for peroxy radicals, was the recycling of HO2 radicals to OH. This reaction was responsible for the recycling of more than 45x106 molecules cm-3 s-1 on two days. The most important sink for OH, and the largest source of peroxy radicals, was the oxidation of NMHCs, in particular, of isoprene and the monoterpenes.
Die vorliegende Arbeit liefert einen Beitrag zum Verständnis der Rolle des RO x bei der troposphärischen Ozonbildung. Troposphärisches Ozon (O 3 ) spielt eine wichtige Rolle bei der Selbstreinigung der Atmosphäre. Andererseits führen erhöhte Ozonkonzentrationen zu gesundheitlichen Beeinträchtigungen beim Menschen und Schäden an Pflanzen und Umwelt. Die Anwesenheit von flüchtigen organischen Verbindungen (VOCs) führt zur Bildung von Peroxyradikalen (RO x ), die das normale photochemische Gleichgewicht zwischen Ozon und Stickoxiden zu Gunsten erhöhter OzonKonzentrationen verschieben. Im Rahmen der Arbeit wurde ein chemischer Verstärker zur Messung der GesamtPeroxyradikalkonzentration gebaut. RO x reagiert im Einlass des Gerätes mit hinzugefügtem NO und CO in einer Kettenreaktion und bildet dabei NO 2 . Dieses wird mit einem Luminoldetektor nachgewiesen. Der Detektor wird alle 2 Stunden kalibriert. Die Kettenlänge wird durch eine Kalibrierung des Gerätes mit HO 2 Radikalen bestimmt, die durch die Photolyse von H 2 O gebildet werden. Der Verstärkungsfaktor wurde in Bezug auf eine Querempfindlichkeit gegen Wasserdampf korrigiert. Die Messgenauigkeit ist etwa 70% bei 60% relativer Feuchte. Messungen am Taunus Observatorium auf dem Kleinen Feldberg in den Sommermonaten der beiden Jahre 1998 und 1999 werden vorgestellt. Die Ozon und RO x Konzentrationen sind gut miteinander korreliert. Allerdings ist die Tagestemperatur die für die Ozon und RO x Konzentrationen bei weitem wichtigste Einflussgröße und ist daher der beste Parameter zur statistischen Beschreibung von photochemischen Vorgängen. Auf der Grundlage der Messungen am Kleinen Feldberg wurde ein einfaches statistisches Modell zur Vorhersage des Ozonmaximums erstellt. Mit den Parametern Temperatur und Ozonkonzentration am Vortag konnte das statistische Modell bereits 80% der Variation der Ozonkonzentration erklären. Durch die Berücksichtigung der RO x Messungen am Vormittag konnte lediglich eine Verbesserung der erklärten Varianz um 0.5% erzielt werden. Um einen Hinweis auf den Einfluss anthropogener Emissionen zu bekommen, wurde der Wochengang von Ozon, RO x und NO x ebenfalls untersucht. Die Zunahme des Ozonmischungsverhältnisses am Wochenende bei gleichzeitigem Rückgang des Mischungsverhältnisses der Stickoxide wird damit erklärt, dass am Kleinen Feldberg eine VOClimitierte Situation vorgefunden wurde. Die Ozonbildungsrate auf Basis der Reaktion zwischen RO x und NO wurde für Tage mit einem Maximum der Globalstrahlung über 600 W m tdatensatz niedrig (r = 0,46). Die beobachtete Änderung des Ozonmischungsverhältnisses wurde mit dem berechneten mittleren Tagesgang der Ozonbildungsrate verglichen. Die Ozonbildungsrate lag um die Mittagszeit bei etwa 5 ppbv h Verlustprozesse zu erklären. Am Abend werden etwa 2 ppbv O 3 pro Stunde abgebaut. Im Rahmen einer Messkampagne im Juni/Juli 2000 am Meteorologischen Observatorium Hohenpeißenberg fanden Messungen der Konzentrationen von RO x , OH, einer Reihe von VOCs, und anderen relevanten Spurengasen statt. Die Messdaten werden mit Hilfe eines auf der Annahme des lokalen photostationären Gleichgewichts der Radikale basierenden Modells interpretiert. Die Modellergebnisse stimmten sehr gut mit den Messungen überein. Die Überschätzung der Konzentration an 2 Tagen wurde durch den Einfluss sauerstoffhaltiger VOCs erklärt. Das '' Recycling" der HO 2 Radikale (die Reaktion zwischen HO 2 und NO) ist die wichtigste Quelle für OH und die wichtigste Senke für RO x . Durch die erhöhte NOKonzentration am Vormittag wird HO 2 sehr schnell in OH umgewandelt, das wiederum für die VOCOxidation und RO x Bildung verantwortlich ist. Die wichtigste OHSenke und RO x Quelle ist die Oxidation von Isopren und den Terpenen. Um die Rolle der photochemischen Ozonbildung auf regionaler Skala zu untersuchen, wurden Ozonmessungen aus ganz Deutschland auf unterschiedlichen zeitlichen und räumlichen Skalen statistisch untersucht. Die Netto Änderungsrate der Ozonkonzentration war tagsüber an 3 nahe zusammenliegenden Stationen sehr ähnlich. Die OzonMessdaten von 277 deutschen Messstationen wurden mit den an einer Waldmessstelle nahe Königstein gemessenen Ozonwerten korreliert. Die Ozonmessungen in Königstein erklären 50% der Varianz der sommerlichen Ozonmessungen zwischen 11:00 und 16:00 MEZ an Stationen, die in einem Umkreis von etwa 250 km von Königstein liegen. Auf das ganze Jahr bezogen, liegt diese ''charakteristische Entfernung" bei etwa 350 km. Diese Ergebnisse deuten darauf hin, dass die Prozesse, die einen wichtigen Einfluss auf die Ozonkonzentration ausüben, auf regionalen Skalen von einigen hundert Kilometern aktiv sind. Zusammenfassend lässt sich sagen, dass die gemessenen RO x Konzentrationen mit den aufgrund der Oxidation der VOCs durch OH berechneten Konzentrationen konsistent sind. Obwohl die RO x Konzentationen für die chemische Modellierung von Bedeutung sind, tragen RO x Messungen nur wenig zu einer Verbesserung der Qualität von kurzfristigen statistischen Ozonprognosen bei. Keywords: Ozone, Troposphere, Peroxy Radicals, Free Radicals, Photochemistry, Chemical Amplifier
The International Halocarbons in Air Comparison Experiment (IHALACE) was conducted to document relationships between calibration scales among various laboratories that measure atmospheric greenhouse and ozone depleting gases. Six stainless steel cylinders containing natural and modified natural air samples were circulated among 19 laboratories. Results from this experiment reveal relatively good agreement among commonly used calibration scales for a number of trace gases present in the unpolluted atmosphere at pmol mol−1 (parts per trillion) levels, such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). Some scale relationships were found to be consistent with those derived from bi-lateral experiments or from analysis of atmospheric data, while others revealed discrepancies. The transfer of calibration scales among laboratories was found to be problematic in many cases, meaning that measurements tied to a common scale may not, in fact, be compatible. These results reveal substantial improvements in calibration over previous comparisons. However there is room for improvement in communication and coordination of calibration activities with respect to the measurement of halogenated and related trace gases.
In der Stratosphäre finden eine Reihe von dynamischen und chemischen Prozessen statt, die u.a. den Abbau von Ozon beeinflussen. Um die langfristigen Veränderungen in der Stratosphäre untersuchen zu können müssen die Abhängigkeit dieser Prozesse von Raum und Zeit bekannt sein. In dieser Arbeit wird eine Untersuchung zur Variabilität der Stratosphäre auf der Grundlage der Varianz von Tracern, die in Form der „Equivalent Displacement Height“, kurz: EDH, dargestellt wird, vorgestellt. Die EDH ist tue mit Hilfe des lokalen vertikalen Gradienten normierte lokale Standardabweichung des Mischungsverhältnisses eines Tracers und besitzt die Dimension einer Länge. Durch die Normierung kann die Varianz verschiedener Tracer miteinander verglichen werden. Mit dem Konzept ist allerdings nur die Diagnose der Variabilität möglich und keine Quantifizierung der dafür verantwortlichen Prozesse. Für die Fragestellung werden drei Datensätze ausgewertet. Ein Datensatz ist mit Hilfe eines kryogenen Luftprobensammlers entstanden. Die Berechnungen iii dieser Arbeit zeigen, dass die zeitliche und räumliche Abdeckung dieses Datensatzes zu niedrig ist, um mit ihm eine repräsentative Aussage über die Varianz von Spurengasen in der Stratosphäre treffen zu können. Eine bessere zeitliche und räumliche Abdeckung besitzt der Datensatz des Satellitenexperimentes HA-LOE. Dieser wird dazu verwendet die monatlichen Verteilungen der mittleren EDH von CH4 und O3 in einem Höhenbereich zwischen 19 und 50 km für einen Zeitraum von 1993 bis 2000 zu berechnen. Die mittlere EDH von OH4 besitzt über den Hemisphären jeweils einen unterschiedlichen Jahresgang. Die Diskussion zeigt, dass dieser hemisphärische Unterschied auf die verschiedenen dynamischen Bedingung in der Stratosphäre über den Hemisphären zurückgeführt werden kann, vor allem auf die Existenz eines stabileren und langlebigeren Polarwirbels in der Südhemisphäre. Im Gegensatz dazu zeigt die mittlere EDH von O3 über beiden Hemisphären einen vergleichbaren Jahresgang, mit minimalen Werten der Varianz während der Sommermonate, wenn die Ausbreitung planetarer Wellen in die Stratosphäre durch die vorherrschende Ostwindzirkulation behindert wird. Dieser Jahresgang steht in Verbindung mit den chemischen und dynamischen Prozessen bzw. der Kombination, welche die Verteilung und Varianz von O3 in der Stratosphäre kontrollieren. Eine eindeutige Trennung der einzelnen Effekte ist dabei allerdings nicht möglich. Der Datensatz des Simulationsmodell KASIMA enthält die Verteilung von CH4 und O3 mit der höchsten zeitlichen und räumliche Abdeckung aller drei Datensätze. Ein Vergleich zwischen den daraus berechneten Verteilungen der mittleren EDH beider Spurengase mit den HALOE-Daten soll helfen, die Varianz welche durch das Modell simuliert wird, mit der gemessenen zu vergleichen. Für das O3 wird eine gute Übereinstimmung zwischen der modellierten und gemessenen Varianz gefunden. Diese guten Übereinstimmungen ergeben sich für CH4 nicht. Aufgrund der unterschiedlichen chemischen Eigenschaften der beiden Tracer wird aus den Ergebnissen geschlossen, dass das Modell die chemischen Prozesse besser simuliert als den atmosphärischen Transport. Mit Hilfe von drei Fallstudien werden weitere Möglichkeiten aufgezeigt. die mit dem Konzept und den Datensätze von HALOE und KASIMA noch bestehen. In der ersten Fallstudie werden anhand der Verteilungen der EDH von CH4 aus dem März 1996 und 1997 die Auswirkungen vorm zwei unterschiedlichen meteorologischen Situation diskutiert, wobei ein eindeutiger Zusammenhang festgestellt wird. In einer zweiten Fallstudie wird der Frage nachgegangen, ob die Normierung auf den vertikalen Gradienten bei der Berechnung der EDH sinnvoll ist, da horizontale Transportprozesse in der Stratosphäre dominieren. Es wird daher zum Vergleich die „Equivalent Displacement Length (EDL)“ von CH4 berechnet, bei der eine Normierung der Varianz auf den horizontalen Gradienten erfolgt. In der dritten Fallstudie wird die Verteilung der mittleren EDH von N20, welche ebenfalls mit dem Datensatz von KASIMA berechnet worden ist, mit der von CH4 verglichen.
Strong perturbations of the Arctic stratosphere during the winter 2002/2003 by planetary waves led to enhanced stretching and folding of the vortex. On two occasions the vortex in the lower stratosphere split into two secondary vortices that re-merged after some days. As a result of these strong disturbances the role of transport in and out of the vortex was stronger than usual. An advection and mixing simulation with the Chemical Lagrangian Model of the Stratosphere (CLaMS) utilising a suite of inert tracers tagging the original position of the air masses has been carried out. The results show a variety of synoptic and small scale features in the vicinity of the vortex boundary, especially long filaments peeling off the vortex edge and being slowly mixed into the mid latitude environment. The vortex folding events, followed by re-merging of different parts of the vortex led to strong filamentation of the vortex interior. During January, February, and March 2003 flights of the Russian high-altitude aircraft Geophysica were performed in order to probe the vortex, filaments and in one case the merging zone between the secondary vortices. Comparisons between CLaMS results and observations obtained from the Geophysica flights show in general good agreement. Several areas affected by both transport and strong mixing could be identified, allowing explanation of many of the structures observed during the flights. Furthermore, the CLaMS simulations allow for a quantification of the air mass exchange between mid latitudes and the vortex interior. The simulation suggests that after the formation of the vortex was completed, its interior remaind relatively undisturbed. Only during the two re-merging events were substantial amounts of extra-vortex air transported into the polar vortex. When in March the vortex starts weakening additional influence from lower latitudes becomes apparent in the model results. In the lower stratosphere export of vortex air leads only to a fraction of about 5% polar air in mid latitudes by the end of March. An upper limit for the contribution of ozone depleted vortex air on mid-latitude ozone loss is derived, indicating that the maximum final impact of dilution is on the order of 50%.
Strong perturbations of the Arctic stratosphere during the winter 2002/2003 by planetary waves led to enhanced stretching and folding of the vortex. On two occasions the vortex in the lower stratosphere split into two secondary vortices that re-merged after some days. As a result of these strong disturbances the role of transport in and out of the vortex was stronger than usual. An advection and mixing simulation with the Chemical Lagrangian Model of the Stratosphere (CLaMS) utilising a suite of inert tracers tagging the original position of the air masses has been carried out. The results show a variety of synoptic and small scale features in the vicinity of the vortex boundary, especially long filaments peeling off the vortex edge and being slowly mixed into the mid latitude environment. The vortex folding events, followed by re-merging of different parts of the vortex led to strong filamentation of the vortex interior. During January, February, and March 2003 flights of the Russian high-altitude aircraft Geophysica were performed in order to probe the vortex, filaments and in one case the merging zone between the secondary vortices. Comparisons between CLaMS results and observations obtained from the Geophysica flights show in general good agreement.
Determining how the elevation of the Northern Andes has evolved over time is of paramount importance for understanding the response of the Northern Andes to deformational and geodynamic processes and its role as an orographic barrier for atmospheric vapor transport over geologic time. However, a fundamental requirement when using stable isotope data for paleoaltimetry reconstructions is knowledge about the present-day changes of δ18O and δD with elevation (isotopic lapse rate). This study defines the present-day river isotopic lapse rate near the Equator (∼3°S) based on analysis of δ18O and δD of surface waters collected from streams across the Western Cordillera and the Inter-Andean depression in Southern Ecuador. The results for the two domains show a decrease of δ18O with elevation which fits a linear regression with a slope of −0.18‰/100 m (R2 = 0.73, n = 83). However, we establish a present-day lapse rate of −0.15‰/100 m for δ18O (R2 = 0.88, n = 19) and -1.4‰/100 m for δD (R2 = 0.93, n = 19) from water samples collected along the west facing slopes of the Western Ecuadorian Cordillera which is mainly subject to moisture transport from the Pacific. We argue that this empirical relationship, consistent with those obtained in different tropical areas of the world, can inform stable isotope paleoaltimetry reconstructions in tropical latitudes.
The Early Permian coal is of great value in the Tengxian Coalfield, Shandon Province, Eastern China. This work deals with the new data focusing on mineralogical characteristics in the Early Permian Shanxi Formation No. 3 coal from the Jinyuan Mine. The Jinyuan coal is a low ash and highly volatile A bituminous coal. Minerals in the No. 3 coal mainly comprise of kaolinite, ankerite, illite, calcite, siderite, and quartz, with varying compositions of trace amounts of pyrite, jarosite, bassanite, anatase, and rutile. According to mineral assemblage in the coal plies, three Types (A to C) can be identified in the No. 3 coal. The dominant minerals in Type A are poorly-ordered kaolinite, illite, quartz, pyrite, and jarosite. Type B is mainly composed of well-ordered kaolinite, illite, siderite, ankerite, and calcite. Type C, with just one sample (JY-3-7c), which contains high proportions of calcite (54%) and ankerite (34%). Terrigenous minerals are elevated in coal plies that typically have relatively high contents of ash yield. The formation of syngenetic pyrite was generally due to seawater, while the sulphate minerals (jarosite and coquimbite) were derived from the oxidation of pyrite. Epigenetic vein-like or fracture-fillings carbonate minerals (ankerite, calcite, and siderite), kaolinite, and pyrite, as well as authigenic quartz were derived from the influx of hydrothermal fluids during different periods, from the authigenic to epigenetic. The paragonite in the coal may have been formed by the precipitated from Na-rich hydrothermal fluids. No effects of magmatic intrusion on mineralogy were investigated in this research.
Die Studie befasst sich mit Formenschatz, Sedimenten und Böden des Komadugu-Flusssystems. Neben einer grundsätzlichen Inventarisierung des bislang kaum erforschten Landschaftskomplexes lag der Schwerpunkt auf der Rekonstruktion von Systemveränderungen im Kontext des spätquartären Klimawandels. So sind die schmalen rezenten Auen teilweise in eine weitgespannte reliktische Überschwemmungsebene eingeschnitten, die möglicherweise synchron zu ehemaligen früh- bis mittelholozänen Tschadsee-Maxima bei Rückstau der Flüsse außerhalb der prominenten Bama-Beach-Ridge-Begrenzung entstand. Während die rezente Aue ein deutlich ausgeprägtes Mäandersystem aufweist, liegen in der Paläoschwemmebene komplexere fluviodeltaische Strukturen mit fließenden Übergängen der klassischen Gerinnebettmuster vor, deren häufige sprunghafte Verlagerung unter Ausräumung und Wiederverfüllung sich auch in der fluvialen Architektur des älteren Alluviums widerspiegelt. Bei Korngrößenanalysen ergab sich eine generelle Dominanz gut sortierter, feinsandiger Substrate. Darüber hinaus reflektieren die rezenten Alluvionen mit schluffigen Hochflut-, feinsandigen Uferbank- und mittel- bis grobsandigen Flussbettsedimentabfolgen sowie feinsandigen bis tonigen Gerinnefüllungen an Altarm-Standorten die fraktionierte Sedimentation in der modernen Aue. Demgegenüber sind die gradierten, feinsandigen Gerinnebett- und gerinnebettnahen Ablagerungen der Terrasse mit ihren äolisch überprägten Tops recht uniform ausgeprägt. Es zeichnen sich jedoch bestimmte Körnungsprovinzen ab, indem im Westen vor allem Feinstsande und Grobschluffe, in östlicher Richtung dann zunehmend sehr gut sortierte grobe Feinsande vertreten sind, wobei letztere aufgearbeitete lokale Dünensande repräsentieren. Der enge genetische Zusammenhang zeigt sich auch in Kornformen, Oberflächenbeschaffenheit und Schwermineralbestand der Sande, die von einer generellen Überlagerung der Transportmechanismen und polyzyklischen Aufarbeitung künden. Die Klimaxböden der östlichen Terrasse stellen offenbar luvic Arenosols/weakly leached ferruginous tropical soils dar, wenngleich aufgrund jüngerer Translokationsprozesse, ebenso wie im Westteil, lithomorphe Braunerden vorherrschen. Die Mehrzahl der durchgeführten OSL-Datierungen weist auf die Sedimentation des älteren Alluviums zur Wende des Pleistozäns zum Holozän hin. Sie markiert den geomorphologisch besonders aktiven Umbruch von ariden zu humiden Bedingungen, der im Einzugsgebiet des Komadugu spätestens gegen 12,5 ka erfolgte. Damit steht das fluviale Verhalten im ehemaligen Unterlaufbereich des Yobe-Systems in einem klaren Gegensatz zu einem für den trockenzeitlich-feuchtzeitlichen Übergang oftmals diagnostizierbaren morphodynamischen Wandel von instabilen zu stabilen Verhältnissen. Die zahlreichen wenig festgelegten Paläofließrinnen und feinsanddominierte Lithofazies als mutmaßliches Resultat einer durch Schichtfluten ausgelösten Dünenpediplanation künden von einem schwankendem, teilweise hoch energetischen Abflussverhalten, wie es am ehesten unter einem längerfristig wechselfeuchten Klimaregime vorgeherrscht haben könnte. Demgegenüber war die fluviale Formung zur Zeit der vollhumiden Maxima des Früh- und Mittelholozäns stark eingeschränkt, wobei es weder zu einer großflächigeren Sedimentation quasi-lagunaler Fazies noch zu kräftigeren Bodenbildungen kam. Die Einschneidung der rezenten Aue fand schließlich im Anschluss an das mittelholozäne Optimum bei Einsatz einer fortschreitenden Aridisierung statt.
The East African Rift System (EARS) was initiated in the Eocene epoch between 50 and 21 Ma probably due to the influence of mantle plumes that caused volcanism, flood basalts and rifting extensions in Ethiopa and the Afar region. As a result of magmatic intrusions and adiabatic decompression melting within the lithosphere caused by the impact of the Kenya plume, there was a southward propagation of the EARS of about 30 – 15 Ma from Ethiopia to Kenya, which coincide with the occurrence of volcanism. The EARS developed towards the south along the margins of the Tanzania Craton between 15 and 8 Ma. Previous findings of low-velocity anomalies within the upper mantle and the mantle transition zone indicate an upwelling of hot mantle material in the vicinity of the Afar region and the East African Rift. This study includes the analysis of P- and S-receiver functions in order to determine further impacts on the lithosphere from below. The aim was to determine the topographic undulations of further boundary layers and to identify their variability owing to the rifting processes and the formation of the EARS. The study area included the Tanzania Craton and the surrounding rift branches of the East African Rift System.
The region of the Rwenzori Mountains can be analysed in detail because of the large dataset of the RiftLink project. The use of the P-receiver function technique and the H-K stacking method enabled to determine different vP /vS ratios depending on the tectonic setting in the Rwenzori region: Rift shoulders (vP /vS =1.74), Albert Rift segment (vP /vS =1.80), Edward Rift segment (vP /vS =1.87) and Rwenzori Mountains (vP /vS =1.86). To determine the topography of the Moho, it is necessary to take into account the thickness of the sedimentary layer, the surface topography, the azimuthal variations in crustal thickness and the impact of local anomalies. After correcting these effects on the Moho depths, significant variations in Moho topography could be determined. The Moho depths range from 29 to 39 km beneath the rift shoulders of the Albertine Rift. Within the rift valley, the crustal thickness varies between 25 – 31 km in the Edward Rift segment and 22 – 30 km in the Albert Rift segment. An averaged crustal thickness of about 26 km within the rift valley indicates the lack of the crustal root beneath the Rwenzoris. Similar variations in crustal thickness were determined by using an automatic procedure for analysing S-receiver functions that was developed in this study.
The S-receiver functions are created by applying a rotation criterion in order to rotate the Z, N and E components into the L, Q and T components. It is necessary to perform trial rotations using different incident and azimuth angles to determine the correct rotation angles. The latter are identified by the use of the rotation criterion, including the amplitude ratio of the converted Moho signal to the direct S/SKS-wave signal. The L component is rotated correctly in the direction of the incident shear wave in the case of the maximum amplitude ratio. After analysing the frequency content of the receiver functions in order to sort out harmonic and long-periodic traces, the individual Moho signals are checked for consistency in order to remove atypic signals. To increase the signal-to-noise ratios on the traces, the S-receiver functions are stacked. For this purpose, the signals of the direct shear waves must originate from similar epicenters. On the basis of similar ray paths, the receiver functions show comparable waveforms and converted signals. To perform the stacking procedure, it is necessary to merge the datasets of the adjacent stations in order to obtain a sufficient number of receiver functions. This analysis is based on the assumption that the incident seismic waves arriving at the adjacent stations penetrate to some extent the same underground structures in the case of similar wave propagation paths. This approach accounts for the fact that the converted signals do not result exclusively from the piercing points at the boundary layers. Further signals originate from the conversions at the boundary layer within the Fresnel Zone. The piercing points are derived from the significant signals in the receiver functions. Depending on the order of arrival of the converted phases on the traces, the signals are attributed to the theoretical discontinuities DIS1, DIS2, DIS3 and DIS4. However, partly due to the low signal-to-noise ratios on the traces, it is difficult to identify the real conversions on the traces and to ensure that the converted signals are attributed to the correct boundary layers. For this reason, it is necessary to check the consistency of the conversion depths among each other. In the case of inconsistent conversion depths, the corresponding signals are either adjusted to another seismic boundary layer or removed from the dataset. To verify the functionality of the automatic procedure and to determine the resolvability with respect to two boundary layers, several models are tested including horizontal and dipping discontinuities. To resolve distinct discontinuities, their depths must differ by at least 60 km, otherwise, due to similar depth ranges of the different boundary layers, the converted signals cannot be separated from each other. As a consequence, the converted signals that originate from different discontinuities are attributed to a single one. Further tests including break-off edges of seismic discontinuities are performed to check the attributions of the converted signals to the discontinuities. Owing to the varying number of boundary layers, the converted signals cannot be attributed to the discontinuities according to the order of their arrivals on the traces. It is necessary to correct their attributions to the seismic discontinuities in order to resolve the boundary layers.
The crust-mantle boundary and further discontinuities within the lithospheric mantle are investigated by applying this automatic procedure. Depending on the tectonic setting, the conversion depths of the Moho range from about 30 – 45 km beneath the western rift shoulder to 20 – 35 km within the rift valley up to 30 – 40 km beneath the eastern rift shoulder. The long wavelengths of the shear waves hamper the correct identification of the converted phases in the S-receiver functions. With respect to the relative differences in conversion depth, the topographic undulations of the crust-mantle boundary are consistent with the Moho depths derived from P-receiver functions. In contrast to the Rwenzori region, it is difficult to resolve completely the trend of the Moho in the remaining area of the East African Rift due to the small dataset provided by IRIS. The results exibit an increase in crustal thickness to up to 45 km in the region of the Cenozoic volcanics such as Virunga, Kivu, Rungwe and Kenya. The greatest Moho depths of more than 50 km are located near Mount Kilimanjaro. In addition to the Moho, the analysis of the S-receiver functions revealed two further boundary layers at depths of 60 – 140 km and 110 – 260 km, which are associated with a mid-lithospheric discontinuity and the lithosphere-asthenosphere boundary, respectively. The shallowest conversion depths of the LAB are focussed to small-scale regions within the rift branches, namely the northern Albertine Rift, the Chyulu Hills and the Mozambique Belt, which are located around the Tanzania Craton. The larger thickness of the lithosphere beneath the cratonic terrain indicates that the Tanzania Craton is not significantly eroded. However, there are indications that the lithosphere beneath the craton and the rift branches is penetrated by ascending asthenospheric melts to depths of up to 140 and 60 km, respectively. The top of the ascending melts is associated with the occurrence of the mid-lithospheric discontinuity. The shallowest conversion depths of this boundary layer (60 – 90 km) are related to the rifted areas of the EARS and the Cenozoic volcanic provinces, which are located along the Albertine Rift, the Kenya Rift and the Rukwa-Malawi rift zones. The deepest conversion depths of up to 140 km are related to the Rwenzori Belt, the Ugandan Basement Complex and the interior of the Tanzania Craton.
Occurrence and sources of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD) in the aquatic environment
(2011)
The aim of the present study was to identify the sources of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD) into the aquatic environment and to investigate its occurrence in rivers and wastewater treatment plants (WWTPs). Therefore, TMDD was analyzed in 441 wastewater samples from influents and effluents of 27 municipal WWTPs, in 6 sludge samples, in 52 wastewater samples from 3 sewage systems of municipal WWTPs, in 489 surface samples from 24 rivers, in 9 wastewater samples of 3 paper-recycling industries and in 65 groundwater samples. TMDD was also analyzed in household paper products, in 23 samples of toilet
papers, in 5 types of paper towels and in 12 types of paper tissues. The samples were collected between 2007 and 2011. The water samples were extracted with solid phase extraction (SPE) and the household paper samples with Soxhlet extraction. Gas chromatography-mass spectrometry (GC-MS) was used for quantification purposes. Between November 2007 and January 2008, TMDD was detected in the river Rhine at Worms with permanent high concentrations (up to 1330 ng/L). The results showed that TMDD is uniformly distributed across the river at Worms. An increase of the mean TMDD concentration from approximately 500 ng/L to 1000 ng/L was registered in January 2008. Due to the minor fluctuations of the TMDD concentration during the sampling period it is expected that the input of TMDD into the river is continuous. Therefore, TMDD might rather originate from effluents of municipal WWTPs than from temporal sources. The mean TMDD load based on the analysis of 147 water samples collected in the River Rhine was 62.8 kg/d which is equivalent to 23 t/a suggesting that TMDD must be used and/or produced in high quantities in order to be found in those high concentrations. To determine if TMDD is discharged by effluents of municipal WWTPs into the rivers, 24 hours influent and effluent samples of four municipal WWTPs in the Frankfurt/Rhine-Main metropolitan region were collected during November 2008 and February 2010 and analyzed for TMDD. The TMDD influent concentrations varied between 134 ng/L and 5846 ng/L and the effluent concentrations between <LOQ (limit of quantitation) and 3539 ng/L. The TMDD elimination rates in the four WWTPs varied between 33% and 68%. The results showed that effluents of municipal WWTPs are an important source of TMDD in the aquatic environment because TMDD is not completely removed from the sewage during the wastewater treatment. Weekly and daily variations of the TMDD concentration in the influents of two municipal WWTPs indicated that both private households and indirect industrial dischargers contribute to the introduction of TMDD into the municipal sewage systems. A more detailed study of the TMDD elimination rate in the different wastewater treatment stages was carried out in the WWTP Niederrad/Griesheim in Frankfurt am Main. The results showed that the removal of TMDD is mainly carried out during the aerobic biological treatments, where the elimination rate was 46%. In contrast, during the anoxic treatment the removal efficiency was only 1.4% and during the mechanical treatment the elimination rate was 19%. To determine the sources of TMDD in the sewage, household paper products (paper tissues, toilet papers and paper towels) were analyzed for TMDD using Soxhlet extraction. TMDD was detected in 83% of the samples (n=40). The highest mean TMDD concentrations were found in recycled toilet paper (0.20 μg/g) and in paper towels (0.11 μg/g). In paper tissues and non-recycled toilet paper the mean TMDD concentrations were lower 0.080 μg/g and 0.025 μg/g respectively. According to these results the high TMDD influent concentrations found previously in municipal WWTPs (mean 1.20 μg/L) cannot be explained due to migration of TMDD from the household paper products into the sewage. Thus indirect industrial dischargers are the cause of the high influent TMDD concentrations. Effluents of municipal WWTPs with different indirect industrial dischargers (textile-, metal processing-, food processing-, electroplating-, paper-recycling- and printing ink factories) were analyzed. The highest mean TMDD concentrations were found in the effluents of municipal WWTPs that have paper-recycling (71.3 μg/L) and printing ink factories (138 μg/L) as indirect industrial dischargers. These results were confirmed by analyzing process wastewater of three paper-recycling factories located in Germany. High TMDD concentrations were detected and fluctuated between 1.83 μg/L and 113 μg/L. TMDD was also analyzed in the wastewater of a non-recycling-paper factory but its concentration was much lower (0.066 μg/L) indicating that TMDD is introduced into the processing water during the papermaking process due to the use of waste paper. Analyses of wastewater samples from different parts of the sewage pipes of a municipal WWTP in Hesse, which receives the wastewater from a printing ink factory, were carried out. The TMDD concentration in the wastewater sample from the sewage pipe of the printing ink factory was much higher (3,300 μg/L) than the TMDD concentration detected in the other wastewater samples from the sewage system (0.030 μg/L – 0.89 g/L). These results confirm the printing ink production as one of the principal sources of TMDD in the sewage. Analysis of surface water samples of the River Modau downstream from the effluent of the WWTP Nieder-Ramstadt showed TMDD concentrations of up to 28.0 μg/L. These high TMDD concentrations might be caused by the indirect wastewater discharges of a paint factory connected to the municipal sewage system. These results indicate that TMDD is introduced into the municipal WWTPs principally by indirect industrial dischargers and they are mainly paint and printing ink factories. The paper-recycling factories also represent an important source of TMDD in municipal WWTPs but indirectly. According to statements given by the representatives of two paper recycling factories neither TMDD or any other TMDD containing product is used or added during the papermaking process. Therefore, TMDD is washed out from the printing inks of the coloured waste paper and concentrated in the process wastewater in the closed water circuits of paper-recycling factories reaching rivers and municipal WWTPs. The occurrence and distribution of TMDD in surface waters in Germany was also studied. The results showed that TMDD is widely distributed across different rivers systems in the federal states of Hesse, North-Rhine-Westphalia, Bavaria, Baden-Wuerttemberg and Rhineland-Palatinate. In Hesse, TMDD was detected in the some of main rivers with mean concentrations of 812 ng/L (Schwarzbach, Hessian Ried), 374 ng/L (Kinzig), 393 ng/L (Main, at Frankfurt), 539 ng/L (Werra), 326 ng/L (Fulda), 151 ng/L (Emsbach) and 161 ng/L (Nidda). In small rivers (creeks) the mean TMDD concentrations varied between <LOQ (Diemel, Urselbach) and 1890 ng/L (Darmbach). The results showed that the TMDD concentrations in creeks are highly influenced by both effluents of WWTPs and by the distance between the sampling point and the nearest WWTP. Surface samples from sampling locations downstream from WWTPs dischargers showed higher TMDD concentrations (mean 518 ng/L) than sampling locations upstream from WWTPs dischargers (mean 35.1 ng/L). The behavior of TMDD during bank filtration was investigated at two locations, at a water utility company at the Lower River Rhine (urban area) and at the Oderbruch polder (rural area). The results indicated that TMDD is removed from the surface water by bank filtration at both sampling locations. The removal process is probably carried out in the first meters of the aquifer (hyporheic zone) by biodegradation processes, since TMDD does not tend to be absorbed by sediments and it was not found in the groundwater of monitoring wells. In groundwater samples from the Hessian Ried (n=23) TMDD was found only in five samples and the highest TMDD concentration was 135 ng/L. According to these results, TMDD does not represent a concern for drinking water in Germany, since it does not reach the groundwater with high concentrations and it has a low toxicity potential. The input of TMDD into the North Sea was estimated to be 60.7 t/a by considering the mean transported loads of TMDD by the River Rhine at Wesel (58.3 t/a) and Meuse in the Netherlands (2.40 t/a). The estimated discharge of TMDD by German municipal WWTPs (8.19 t/a) and paper-recycling factories (9.24 t/a) into rivers seems to be too low considering that the mean TMDD load in the River Rhine downstream from Wesel is 58.3 t/a. However, due to the high density of population and industries at the Lower Rhine it is expected that more relevant sources of TMDD are located along the Rhine River increasing the transported load. According to the results of this PhD project TMDD is a non-ionic surfactant contained in products, which are applied on surfaces (printing inks and paints) and has the potential to reach the aquatic environment. Therefore, TMDD should fulfill the requirement of a biodegradability of 80% established by the “Law on the Environmental Impact of Detergents and Cleaning Products” in Germany. However, due to the partial elimination rates of TMDD obtained in municipal WWTPs (between 33% and 68%) and to the absence of information about the execution of the biodegradation test on TMDD, it is unknown if TMDD is in accordance with this law. Otherwise, its use as surfactant in such products is questionable.
Highlights
• We find DBrfluid/melt = 1.19 to 3.92 for experimental Br degassing from basalt magma into aqueous fluids.
• D <1 under almost dry conditions propose only little Br degassing for dry intra-plate volcanism relative to volcanic arcs.
• An annual global Br flux of 23.5–72.9 × 109 g/y into the atmosphere was calculated.
Abstract
We present the first in-situ partitioning data for bromine between a natural basaltic melt and a coexisting fluid. For this study hydrothermal diamond anvil cell experiments at pressures up to 1.7 GPa were conducted. We combined laser heating to melt the basalt glass with external heating to lower the temperature gradient in the cell and to initiate circulation for the aqueous fluid. Bromine concentrations were measured in-situ with X-ray fluorescence in the basaltic melts, glasses, and in the fluid. From the results we calculated partition coefficients of DBrfluid/melt = 1.19 to 3.92 in the range of 0.4 to 1 GPa for aqueous fluids. Experiments with neon as the surrounding fluid (DBrfluid/melt = 0.38 ± 0.01 at 1.1 GPa) suggest that Br-release from a basalt into volatiles that have no bonding affinity with Br is weak. This should be the case for dry intra-plate volcanic eruptions. From the experimentally gained partition coefficients and from global Br concentration values in melt inclusions of arc magmas, we calculated an annual global Br flux of 23.5–72.9 × 109 g/y.
We present a new experimental dataset on the impact of the heavy halogens chlorine, bromine and iodine on the Raman water bands concerning pressure and their concentration at room temperature. These experiments were conducted at ambient temperature, with variations in halogen concentration and pressure ranging from 0 to 1.4 GPa.
The strength of the Raman water band shift change increases with the ionic size from chlorine, over bromine, to iodine. Our experiments further demonstrate that increased pressure diminishes the impact of the halogen shift change to a varying extent for each of the three halogens. This finding can have significant implications for the salinity calculation of fluid inclusions in minerals such as quartz or olivine. Particularly in the low salinity range, the concentration can be markedly underestimated if the pressure effect is neglected. For experiments in diamond anvil cells involving halogens dissolved in water, the change in Raman water band shifts can serve either as a new tool to monitor pressure, or to monitor the salinity.
The Match method for the quantification of polar chemical ozone loss is investigated mainly with respect to the impact of the transport of air masses across the vortex edge. For the winter 2002/03, we show that significant transport across the vortex edge occurred and was simulated by the Chemical Lagrangian Model of the Stratosphere. In-situ observations of inert tracers and ozone from HAGAR on the Geophysica aircraft and balloon-borne sondes, and remote observations from MIPAS on the ENVISAT satellite were reproduced well by CLaMS. The model even reproduced a small vortex remnant that remained a distinct feature until June 2003 and was also observed in-situ by a balloon-borne whole air sampler. We use this CLaMS simulation to quantify the impact of transport across the vortex edge on ozone loss estimates from the Match method. We show that a time integration of the determined vortex average ozone loss rates, as performed in Match, results in a larger ozone loss than the polar vortex average ozone loss in CLaMS. The determination of the Match ozone loss rates is also influenced by the transport of air across the vortex edge. We use the model to investigate how the sampling of the ozone sondes on which Match is based represents the vortex average ozone loss rate. Both the time integration of ozone loss and the determination of ozone loss rates for Match are evaluated using the winter 2002/2003 CLaMS simulation. These impacts can explain the majority of the differences between CLaMS and Match column ozone loss. While the investigated effects somewhat reduce the apparent discrepancy in January ozone loss rates reported earlier, a distinct discrepancy between simulations and Match remains. However, its contribution to the accumulated ozone loss over the winter is not large.
The Match method for quantification of polar chemical ozone loss is investigated mainly with respect to the impact of mixing across the vortex edge onto this estimate. We show for the winter 2002/03 that significant mixing across the vortex edge occurred and was accurately modeled by the Chemical Lagrangian Model of the Stratosphere. Observations of inert tracers and ozone in-situ from HAGAR on the Geophysica aircraft and sondes and also remote from MIPAS on ENVISAT were reproduced well. The model even reproduced a small vortex remnant that was isolated until June 2003 and was observed in-situ by a balloon-borne whole air sampler. We use this CLaMS simulation to quantify the impact of cross vortex edge mixing on the results of the Match method. It is shown that a time integration of the determined vortex average ozone loss rates as performed in Match results in larger ozone loss than the polar vortex average ozone loss in CLaMS. Also, the determination of the Match ozone loss rates can be influenced by mixing. This is especially important below 430 K, where ozone outside the vortex is lower than inside and the vortex boundary is not a strong transport barrier. This effect and further sampling effects cause an offset between vortex average ozone loss rates derived from Match and deduced from CLaMS with an even sampling for the entire vortex. Both, the time-integration of ozone loss and the determination of ozone loss rates for Match are evaluated using the winter 2002/03 CLaMS simulation. These impacts can explain the differences between CLaMS and Match column ozone loss. While the investigated effects somewhat reduce the apparent discrepancy in January ozone loss rates, a discrepancy between simulations and Match remains. However, its contribution to the accumulated ozone loss over the winter is not large.
We present simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS) for the Arctic winter 2002/2003. We integrated a Lagrangian denitrification scheme into the three-dimensional version of CLaMS that calculates the growth and sedimentation of nitric acid trihydrate (NAT) particles along individual particle trajectories. From those, we derive the HNO3 downward flux resulting from different particle nucleation assumptions. The simulation results show a clear vertical redistribution of total inorganic nitrogen (NOy), with a maximum vortex average permanent NOy removal of over 5 ppb in late December between 500 and 550 K and a corresponding increase of NOy of over 2 ppb below about 450 K. The simulated vertical redistribution of NOy is compared with balloon observations by MkIV and in-situ observations from the high altitude aircraft Geophysica. Assuming a globally uniform NAT particle nucleation rate of 3.4·10−6 cm−3 h−1 in the model, the observed denitrification is well reproduced. In the investigated winter 2002/2003, the denitrification has only moderate impact (<=10%) on the simulated vortex average ozone loss of about 1.1 ppm near the 460 K level. At higher altitudes, above 600 K potential temperature, the simulations show significant ozone depletion through NOx-catalytic cycles due to the unusual early exposure of vortex air to sunlight.
We present simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS) for the Arctic winter 2002/2003. We integrated a Lagrangian denitrification scheme into the three-dimensional version of CLaMS that calculates the growth and sedimentation of nitric acid trihydrate (NAT) particles along individual particle trajectories. From those, we derive the HNO3 downward flux resulting from different particle nucleation assumptions. The simulation results show a clear vertical redistribution of total inorganic nitrogen ( ), with a maximum vortex average permanent removal of over 5ppb in late December between 500 and 550K and a corresponding increase of of over 2ppb below about 450K. The simulated vertical redistribution of is compared with balloon observations by MkIV and in-situ observations from the high altitude aircraft Geophysica. Assuming a globally uniform NAT particle nucleation rate of 7.8x10-6cm-3h-1 in the model, the observed denitrification is well reproduced.
In the investigated winter 2002/2003, the denitrification has only moderate impact (≤14%) on the simulated vortex average ozone loss of about 1.1ppm near the 460K level. At higher altitudes, above 600K potential temperature, the simulations show significant ozone depletion through -catalytic cycles due to the unusual early exposure of vortex air to sunlight.
In der "Meteorologischen Zeitschrift" 1900, pag. 140 hat Professor R. Börnstein nachgewiesen, dass der Barometerstand im Laufe eines siderischen Monats (27 1/3 d) eine bestimmte Kurve bildet. Das Material von Berlin, Magdeburg, Potsdam, Wien, Upsala, San Francisco etc. zeigte ein Maximum für das südl., ein Minimum für das nördl, Lunistitium. Die Amplitude betrug bis zu 4 mm. Wir haben dieselbe Untersuchung für den Osnabrücker Barometerstand ausgeführt, und zwar an der Hand von Aufzeichnungen eines selbstregistrierenden Barometers, die uns das "Osnabr. Tagesblatt" in dankenswerter Weise zur Verfügung gestellt hat. Aus den Aufzeichnungen die sich über etwa 26 siderische Monate erstrecken, wurde für jeden Tag des siderischen Monats ein Mittelwert aus je 4 sechs Stunden auseinander liegenden Einzelwerten berechnet, aus den 26 dann wiederum das Mittel genommen.
This is a short movie about the research project No. 297 41 132 of the German Federal Environmental Agency. It is comissioned by the German Ministry for the Environment, Nature Conservation and Nuclear Safety and the German Federal Environmental Agency, Division II 6.2.
The assumption that mankind is able to have an in uence on global or regional climate, respectively, due to the emission of greenhouse gases, is often discussed. This assumption is both very important and very obscure. In consequence, it is necessary to clarify definitively which meteorological elements (climate parameters) are in uencend by the anthropogenic climate impact, and to which extent in which regions of the world. In addition, to be able to interprete such an information properly, it is also necessary to know the magnitude of the different climate signals due to natural variability (for example due to volcanic or solar activity) and the magnitide of stochastic climate noise. The usual tool of climatologists, general circulation models (GCM) suffer from the problem that they are at least quantitatively uncertain with regard to the regional patterns of the behaviour of climate elements and from the lack of accurate information about long-term (decadal and centennial) forcing. In contrast to that, statistical methods as used in this study have the advantage to test hypotheses directly based on observational data. So, we focus to the very reality of climate variability as it has occurred in the past. We apply two strategies of time series analyis with regard to the observed climate variables under consideration. First, each time series is splitted into its variation components. This procedure is called 'structure-oriented time series separation'. The second strategy called 'cause-oriented time series separation' matches various time series representing various forcing mechanisms with those representing the climate behaviour (climate elements). In this way it can be assessed which part of observed climate variability can be explained by this (combined) forcing and which part remains unexplained.
The assumption that mankind is able to have an in uence on global or regional climate, respectively, due to the emission of greenhouse gases, is often discussed. This assumption is both very important and very obscure. In consequence, it is necessary to clarify definitively which meteorological elements (climate parameters) are in uencend by the anthropogenic climate impact, and to which extent in which regions of the world. In addition, to be able to interprete such an information properly, it is also necessary to know the magnitude of the different climate signals due to natural variability (for example due to volcanic or solar activity) and the magnitide of stochastic climate noise. The usual tool of climatologists, general circulation models (GCM) suffer from the problem that they are at least quantitatively uncertain with regard to the regional patterns of the behaviour of climate elements and from the lack of accurate information about long-term (decadal and centennial) forcing. In contrast to that, statistical methods as used in this study have the advantage to test hypotheses directly based on observational data. So, we focus to the very reality of climate variability as it has occurred in the past. We apply two strategies of time series analyis with regard to the observed climate variables under consideration. First, each time series is splitted into its variation components. This procedure is called 'structure-oriented time series separation'. The second strategy called 'cause-oriented time series separation' matches various time series representing various forcing mechanisms with those representing the climate behaviour (climate elements). In this way it can be assessed which part of observed climate variability can be explained by this (combined) forcing and which part remains unexplained.
Basierend auf der Feststellung, daß selbst die aufwendigsten zur Zeit verfügbaren Klimamodelle (das sind gekoppelte atmosphärisch-ozeanische Zirkulationsmodelle, AOGCM) nicht in der Lage sind, alle bekannten externen Antriebe und internen Wechselwirkungen des Klimas simultan zu erfassen, werden zunächst die Stärken und Schwächen von rein statistischen Ansätzen zur Analyse von Zusammenhängen zwischen beobachteten Zeitreihen diskutiert. Speziell geht es dabei um die Frage, welche natürlichen und anthropogenen Antriebe in welchem Ausmaß zu den beobachteten Variationen der globalen Mitteltemperatur beigetragen haben (Signaltrennung). Es wird gezeigt, daß ein einfacher physikalisch motivierter Ansatz, der einige Schwächen der rein statistischen Ansätze vermeidet, nicht zum Ziel der Signaltrennung führt. Damit ergibt sich die Notwendigkeit, sich eingehender mit den Eigenschaften des globalen Klimasystems zu beschäftigen. So stellt sich die Frage, unter welchen Bedingungen das Klima überhaupt vorhersagbar ist. Aufgrund dieser Überlegungen erscheint es möglich, das globale Klima, repräsentiert durch die globale Mitteltemperatur, mit Hilfe von Energie-Bilanz-Modellen (EBM) zu beschreiben. Es folgt, daß ein 3-Boxen-EBM (Atmosphäre, ozeanische Mischungsschicht und tieferer Ozean) ausreicht, um den Verlauf der globalen bodennahen Mitteltemperatur zu untersuchen. Um das Problem einer Überanpassung zu vermeiden, wird das Modell am hemisphärisch gemittelten Jahresgang von Temperatur und Ausstrahlung, am Verlauf der bodennahen Mitteltemperatur eines Zirkulationsmodells im Einschaltexperiment, sowie im Vergleich zu paläoklimatologischen Daten kalibriert. Es wird eine Lösung dieses Modells abgeleitet, die als rekursiver Filter zur Zeitreihenanalyse verwendet werden kann. Um auch den hemisphärischen Temperaturverlauf untersuchen zu können, wird das 3-Boxen-Modell auf fünf Boxen erweitert (hemisphärische Atmosphären- und ozeanische Mischungsschicht-Boxen sowie ein globaler tieferer Ozean). Auch dieses Modell wird im wesentlichen an den Jahresgängen der Temperatur kalibriert und eine Lösung in Form eines rekursiven Filters abgeleitet. Von besonderer Bedeutung ist dabei, daß die so abgeleiteten Filter weder in ihrer Struktur, noch in ihren Parameterwerten aus einer Anpassung an die zu untersuchenden Zeitreihen stammen. Bevor die beobachteten Temperaturzeitreihen für den Zeitraum von 1866 bis 1994 mit den zwei Modellversionen rekonstruiert werden können, müssen die berücksichtigten externen Antriebe in Form von Heizratenanomalien vorliegen. Es werden zwei natürliche (solare Schwankungen und explosive Vulkanaktivität) und zwei anthropogene externe Antriebe (Treibhausgas- und Schwefeldioxidemissionen, die zur Bildung von anthropogenem troposphärischen Sulfat führen) untersucht. Die Heizratenanomalien der solaren Schwankungen folgen aus Satellitenmessungen und einer Extrapolation mit Hilfe von Sonnenflecken-Relativzahlen. Für den Einfluß des Vulkanismus wurde eine Parametrisierung erstellt, die sowohl die Ausbreitung von stratosphärischem Vulkanaerosol als auch dessen Einfluß auf den Strahlungshaushalt berücksichtigt. Zur Beschreibung des anthropogenen Zusatztreibhauseffekts wurde auf Ergebnisse von Strahlungs-Konvektions-Modellen (RCM) zurückgegriffen. Der Einfluß des anthropogenen troposphärischen Sulfats wurde entsprechend dem ungenauen Kenntnisstand nur grob parametrisiert. Mit den Modellen lassen sich zu jedem Antrieb Zeitreihen der globalen und hemisphärischen Temperaturanomalien berechnen. Die beobachteten ENSO-korrigierten Temperaturanomalien lassen sich (außer im Fall der Nordhemisphäre) sehr gut als Summe dieser Antriebe und Zufallsrauschen ausdrücken. Dabei hat das Zufallsrauschen mit dem Modell verträgliche Eigenschaften und kann somit als internes Klimarauschen interpretiert werden. Es ist demnach möglich, zusätzlich zur Signaltrennung zu testen, ob sich die Temperaturzeitreihen ohne die anthropogenen Antriebe signifikant anders verhalten hätten. Der Unterschied ist auf der Südhemisphäre und global mit 99 % signifikant, auf der Nordhemisphäre mit 95 %. Das bedeutet, daß der Mensch das Klima mit hoher Wahrscheinlichkeit beeinflußt. Auf der Basis von Szenarien wird außerdem der anthropogene Einfluß auf das Klima der nächsten Dekaden prognostiziert. In diesem Zusammenhang stellt sich die Frage, wie groß die Zeitverzögerung zwischen anthropogenen Antrieben und deren Wirkung auf das Klima ist. Auch dieser Frage wird nachgegangen und es ergibt sich, daß diese Verzögerung zur Zeit bei etwa zehn Jahren liegt. Da die Verzögerungszeit aber keine Eigenschaft des Klimasystems ist (wie etwa eine Trägheitsoder Mischungszeit), sondern von der zeitlichen Struktur des Antriebs abhängt, ist sie keine Konstante und kann somit nur eingeschränkt für Prognosen verwendet werden. Andererseits erlaubt die Kenntnis der Verzögerungszeit eine statistische Verifikation mit Hilfe eines multiplen Regressionsmodells. Diese unterstützt die Prognosen des EBM.
Im Zusammenhang mit der Diskussion des globalen Klimawandels stellt sich die Frage, ob extreme Wettersituationen wahrscheinlicher werden. Diese Frage ist wegen der Gefahren, die von extremen Wettersituationen ausgehen, weit über die Grenzen der Meteorologie hinaus von Bedeutung. Dennoch findet man in der Fachliteratur sehr wenige Beiträge zu diesem Thema. Dies liegt im wesentlichen daran, dass bei der Analyse von Extremwerten im allgemeinen von konstanten Überschreitungswahrscheinlichkeiten für Schwellwerte ausgegangen wird. Wenn diese Arbeitshypothese wahr ist, können Wiederkehrzeiten einfach als Kehrwert der Eintrittswahrscheinlichkeit angesehen werden. Dann – nur dann - macht der Ausdruck Jahrhundertereignis einen Sinn, der über den Moment hinaus reicht. In diesem Beitrag soll zunächst das Vokabular zur Beschreibung von Extremwerten (hier als Werte oberhalb von Schwellen) vorgestellt bzw. in Erinnerung gerufen werden. Diese werden auf den einfachen Fall stationärer Zeitreihen angewendet, woraus die üblichen vereinfachten Zusammenhänge folgen. Im Anschluss wird ein künstliches Beispiel einer Variable mit veränderlichem Mittelwert untersucht. Dieses zeigt deutlich, wie stark die Kenngrößen des Extremverhaltens von Schwankungen im Mittelwert abhängen können. Bei der Analyse klimatologischer Beobachtungsdaten, steht man vor dem Problem, dass kein einfaches Modell für die Generierung der Zeitreihe zur Verfügung steht, woraus man die Eigenschaften des Extremverhaltens ableiten könnte. Gelingt es jedoch, die Beobachtungen mit Hilfe einfacher empirischer Modellgleichungen hinreichend gut zu beschreiben, so ist der Weg zur Analyse der Extremwerte in instationären Zeitreihen geebnet. Dabei braucht man nicht, wie oft üblich, nur die (relativ wenigen) (Extremwerte für die Analyse des Extremverhaltens heranzuziehen, sondern kann die gesamte von der Zeitreihe zur Verfügung gestellte Information nutzen. Diese Strategie wird exemplarisch an zwei Zeitreihen vorgestellt. Aus Gründen der Einfachheit sind dies Monatsmittel bzw. Jahresmittel der Temperatur. In diesen sind eindeutige Änderungen sowohl im mittleren als auch im extremen Verhalten sichtbar. Daraus kann zwar geschlossen werden, dass sich die Wettersituationen im Laufe der Zeit verändert haben, nicht aber wie. Ein häufigeres Auftreten extremer Mittelwerte kann bedeuten, dass warme Wettersituationen häufiger oder wärmer geworden sind, oder das kalte Wettersituationen wärmer oder weniger geworden sind, oder aber, dass eine Überlagerung verschiedener Veränderungen zu diesem Ergebnis führt. So kann die Frage, ob extreme Wettersituationen wahrscheinlicher werden, in diesem Beitrag nicht abschließend geklärt werden, jedoch wird ein Werkzeug vorgestellt, das geeignet erscheint, diese Frage zu beantworten.
Constructive waterfalls
(1911)
The excavation of valleys by waterfalls is one of the best known and most effective processes by which rivers cut down the surface of the earth. The influence of waterfalls is usually regarded as solely destructive, and as always helping to lower the land. They undermine and cut backward the rock faces over which they fall : by this recession they excavate deep gorges ; and the existence of these gorges enables the adjacent country to be lowered to the level of the valIey floors. The waterfalls, moreover, empty any lakes they rnay reach in their retreat, while the ravines below the falls may drain the springs and thus desiccate the neighbouring hihlands. Observations in various countries had suggested to me that waterfalls may sometimes be constructive in stead of destructive, and that they may reserse their usual procedure, advancing instead of retreating, filling valleys instead of excavating them, and forrning alluvial plains and lakes instead of destroying them. The best illustrations I have seen of such advancing, constructive waterfalls are on some rivers of Dalmatia and Bosnia, where they occur in various stages of development. ...
Im Rahmen dieser Arbeit wurde ein Verfahren zur Messung der Absorption der TM0-Mode im atmosphärischen Wellenleiter entwickelt, das auf der Bestimmung des Amplitudenabfalls von durch Blitze generierten ELF-Impulsen beruht. Eine Anwendung des Verfahrens setzt die simultane Messungen der ELF-Impulse an verschiedenen Stationen voraus. Im Sommer 1998 wurde im Rahmen der Spritekampagne'98 ein geeigneter Datensatz an drei Stationen im Westen Nordamerikas gewonnen. Bislang wurde ein Teil dieses Datensatzes herangezogen, um das Messverfahren zu testen und mit Ergebnissen aus einer anderen Quelle zu vergleichen. Diese Tests waren erfolgreich und die Ergebnisse von Hughes und Gallenberger [10] konnten reproduziert werden. Die Stationen wurden mit Induktionsspulen-Magnetometern vom Typ Metronix MFS05 im HF-Modus betrieben. Die für die Instrumentenkorrektur erforderlichen Übertragungsfunktionen der Magnetometer waren vorab nur für den LF-Modus mit Vertrauen erweckender Sicherheit bekannt. Dies machte eine Nachkalibrierung der Magnetometer erforderlich, bei der zunächst versucht wurde, die bekannte LF-Übertragungsfunktion zu reproduzieren. Dazu wurde die Einspeisung einer Rechteckschwingung in den Kalibriereingang des MFS05-Magnetometers verwendet. Bei 5 von 6 verwendeten Magnetometern ließ sich die Übertragungsfunktion für den LF-Modus reproduzieren. Bei einem traten jedoch deutliche Abweichungen auf, die sich auch bei anderen Messungen reproduzieren ließen. Die Übertragungsfunktion des Magnetometers hat sich also seit der letzten Kalibrierung durch den Hersteller verändert. Erst durch diese Nachkalibrierung ist es möglich geworden, diese Veränderung in Instrumentenkorrekturen einzubringen. Nachdem im LF-Modus gezeigt war, dass die verwendete Kalibrierungsmethode funktioniert wurde sie auch für den HF-Modus angewandt. Neben der Kalibrierung durch Einspeisung eines synthetischen Signals wurden auch Kalibrierungen unter Ausnutzung der natürlichen Anregung durchgeführt. Diese dienten in erster Linie einem Vergleich verschiedener Messgeräte: Den beiden Datenloggern SPAM MkIII und Quanterra QT4120 sowie den bei- den Magnetometern Metronix MFS05 und EMI BF-4. Der QT4120-Datenlogger wurde ursprünglich nicht zum Anschluss von Magnetometern konzipiert und benötigte dazu eine separate Adaptereinheit. Eine solche Adaptereinheit (kurz "Adapterbox") wurde im Rahmen dieser Arbeit konzipiert und gemeinsam mit der am Institut angestellten Elektronikerin Vera Fischer implementiert. Die Messergebnisse der Kalibrierungen mit natürlicher Anregung wurden so gedeutet, dass der SPAM MkIII-Datenlogger und das MFS05-Magnetometer gegenüber dem Quanterra QT4120-Datenlogger und dem EMI BF-4-Magnetometer einen geringeren Rauschpegel im ELF-Bereich aufweisen. Dies muss nicht für Frequenzen unterhalb des ELF-Bereichs gelten - dort wurden keine Untersuchungen angestellt.
Die vorliegende Arbeit behandelt das Forschungsthema der Entstehung des flüssigen Eisenkerns im Zentrum unseres Planeten. Dieses bislang wenig verstandene Gebiet ist reich an Fragestellungen, sowohl für Experimentatoren als auch für die Geodynamik. Es gibt sehr viele Arbeiten, die den Bildungsprozess experimentell untersuchen, jedoch wurde in den letzten Jahren die numerische Untersuchung in diesem Gebiet kaum vorangetrieben. Der experimentelle Teil der Arbeit stellt sich hierbei der aktuellen Frage nach der Perkolationsschwelle
1 von Eisenschmelze in der Silikatmatrix der Protoerde, während numerisch die Effekte von Potenzgesetzkriechen, Dissipation und Schmelzsegregation beim Absinken eines Eisendiapirs nach Ausbildung eines ersten flachen Magmaozeans in der Protoerde behandelt werden. Die genauen Fragestellungen könnnen dabei im letzten Abschnitt der Einleitung gefunden werden.
The region of Talmont-Saint-Hilaire (Vendée, France), located at the contact between the Armorican Massif, the Aquitanian Basin and the Atlantic Ocean, has been studied by many geologists and geographers, over the last three centuries. In the years 1780, silver was mined from the sulphide-bearing ore that occurs at the base of the Jurassic limestones. The stratigraphy of the latter sediments, as well as their relationship with the hercynian basement, was investigated during the 19th and 20th centuries, mainly by Rivière, the author of the first geological map of the area (1838), Cossmann, Vasseur, Péneau, Ters and Butel. As for Gabilly, he considered the anse Saint-Nicolas as a para-stratotype of the Toarcian. A few Authors, mainly Bocquier and Ters, also studied the evolution of the Atlantic coast during Quaternary. They evidenced remnants of several surfaces fashioned by marine abrasion, the age of which was constrained by archaeological studies. In 1963, Gilbert Bessonnat discovered dinosaur footprints, which, however, had already been observed by Bocquier in the years 1930. Montenat and Lapparent studied the occurrence, which proved to be one of the richest in Europe.
Goethes Beschäftigung mit der Erdgeschichte ist von großen Gesten bestimmt, leidenschaftlicher Parteinahme, ästhetischem Anspruch. Sie wird ihm zu einem grundlegenden Baustein der eigenen "Welterschaffung", deren Widerschein sich im zweiten Teil des "Faust" und in der Figur des Montan in "Wilhelm Meisters Wanderjahren" spiegelt. Aber auch unmittelbare Experimentierlust zeichnet die Geschichte seiner Bemühungen um "das Studium des Inneren der Erde" aus - der Erdforscher begibt sich in die Hexenküche des Laboratoriums, etwa um Versuche zu den "metallischen Vegetationen" des "Arbor dianae" durchzuführen, wo es um die Erzeugung von Kristallbildungen von Metallen auf chemischem Weg geht: sie weisen eine gewisse Ähnlichkeit mit baum- und pflanzen ähnlichen Formen auf. Seine Arbeit ist erfüllt von der Freude an der Empirie, aber bei allzu langem Verweilen beim Steineschlagen im Feld stellt sich auch bald Langeweile ein.
Accretion rates of Holocene tropical coral reefs in three areas in the Atlantic, Pacific and Indian Oceans have been quantified in 79 dated core sections in 34 reef cores from Belize, the Maldives and French Polynesia. Holocene vertical reef accretion rate averages 5.05 m/kyr and has decreased during the past 10 kyr. Accretion rates in branched and massive coral facies are statistically similar. Reef accretion rate is positively correlated with the rate of sea‐level rise, that is the degree of creation of accommodation space, and with climate as expressed in a Holocene sea surface temperature anomaly. Accommodation space is also created by subsidence, but at a rate one to two orders of magnitude lower than that created by glacio‐eustasy (0.04 to 0.16 m/kyr). Lagoonal background sedimentation in adjacent reef lagoons averages 0.89 m/kyr as measured in 72 dated core sections in 28 cores. Lagoonal carbonate sedimentation on top of underlying mangrove peat usually starts after a considerable hiatus of ca 3 kyr on average. The lagoonal background sedimentation rate increased during the Holocene, probably due to deepening. The differences between vertical reef accretion and lagoonal background sedimentation rates are a major factor in the production of the widely known saucer shapes typical of tropical reefs and carbonate platforms, that is the creation of unfilled accommodation space. Reef core recovery, used as a proxy for reef consolidation, and core depth exhibit a statistically negative correlation based on data from 326 core barrels. Recovery and marine cement abundance (average volume 8.6%) also decrease from windward to leeward core positions. These observations are presumably a result of both a decrease in the rate of sea‐level rise that is the increase in time available for submarine cementation during the Holocene and the amount of flushing of reef interstices by marine waters.
A massive occurrence of microbial carbonates, including abundant sponge remains, within the Devonian Elbingerode Reef Complex was likely deposited in a former cavity of the fore-reef slope during the early Frasnian. It is suggested that the formation of microbial carbonate was to a large part favored by the activity of heterotrophic, i.e., sulfate-reducing bacteria, in analogy to Quaternary coral reef microbialites. The Elbingerode Reef Complex is an example of an oceanic or Darwinian barrier reef system. In modern barrier reef settings, microbialite formation is commonly further facilitated by weathering products from the central volcanic islands. The Devonian microbialites of the Elbingerode Reef Complex occur in the form of reticulate and laminated frameworks. Reticulate framework is rich in hexactinellid glass sponges, the tissue decay of which led to the formation of abundant micrite as well as peloidal and stromatactis textures. Supposed calcimicrobes such as Angusticellularia (formerly Angulocellularia) and Frutexites, also known from cryptic habitats, were part of the microbial association. The microbial degradation of sponge tissue likely also contributed to the laminated framework accretion as evidenced by the occurrence of remains of so-called “keratose” demosponges. Further typical textures in the microbialite of the Elbingerode Reef Complex include zebra limestone, i.e., the more or less regular intercalation of microbial carbonate and cement. Elevated concentrations of magnesium in the microbialite as compared to the surrounding metazoan (stromatoporoid-coral) reef limestone suggests that the microbialite of the Elbingerode Reef Complex was initially rich in high-magnesium calcite, which would be yet another parallel to modern, cryptic coral reef microbial carbonates. Deposition and accretion of the microbialite largely occurred in oxygenated seawater with suboxic episodes as indicated by the trace element (REE + Y) data.
Tropische Korallenriffe sind die artenreichsten Ökosysteme im Ozean. Die »tropischen Regenwälder der Meere« beherbergen zirka 800 Korallenarten und mehrere zehntausend Arten aus fast allen bekannten Tierstämmen. Korallenriffe bedecken weltweit eine Fläche von 600.000 Quadratkilometern, das sind 0,17 Prozent der Erdoberfläche. Sie treten als nahe der Küste gelegene Saumriffe, küstenfernere Barriereriffe, ringförmige Atolle und flache Karbonat-Plattformen auf . Der Begriff »Karbonat« weist darauf hin, dass Korallen als Riffbildner ein Skelett aus Kalk haben. Auch Kalkalgen und Weichtiere wie Muscheln und Schnecken sind durch die Bildung von Kalkskeletten und Kalkschalen am Riffaufbau beteiligt. Da tropische Korallenriffe nur in der Nähe der Meeresoberfläche wachsen, können Geowissenschaftler mit Hilfe fossiler Korallenfunde ermitteln, wie sich der Pegel des Meeresspiegels in vergangenen Jahrtausenden entwickelt hat. Auch andere wichtige Klimadaten wie Wassertemperatur, Sonneneinstrahlung und Kohlendioxid-Gehalt der Atmosphäre sind in Korallenriffen »gespeichert«. Frankfurter Geowissenschaftler erschließen diese wichtigen Daten, die weit vor menschliche Messungen zurückreichen, durch systematische Bohrungen in Korallenriffen der Karibik, des Persischen Golfs und der Malediven.
The accessories perovskite, pyrochlore, zirconolite, calzirtite and melanite from carbonatites and carbonate-rich foidites from the Kaiserstuhl are variously suited for the in situ determination of their U–Pb ages and Sr, Nd- and Hf-isotope ratios by LA-ICP-MS. The 143Nd/144Nd ratios may be determined precisely in all five phases, the 176Hf/177Hf ratios only in calzirtite and the 87Sr/86Sr ratios in perovskites and pyrochlores. The carbonatites and carbonate-rich foidites belong to one of the three magmatic groups that Schleicher et al. (1990) distinguished in the Kaiserstuhl on the basis of their Sr, Nd and Pb isotope ratios. Tephrites, phonolites and essexites (nepheline monzogabbros) form the second and limburgites (nepheline basanites) and olivine nephelinites the third. Our 87Sr/86Sr isotope data from the accessories overlap with the carbonatite and olivine nephelinite fields defined by Schleicher et al. (1990) but exhibit a much narrower range. These and the εNd and εHf values plot along the mantle array in the field of oceanic island basalts relatively close to mid-ocean ridge basalts. Previously reported K–Ar, Ar–Ar and fission track ages for the Kaiserstuhl lie between 16.2 and 17.8 Ma. They stem entirely from the geologically older tephrites, phonolites and essexites. No ages existed so far for the geologically younger carbonatites and carbonate-rich foidites except for one apatite fission track age (15.8 Ma). We obtained precise U–Pb ages for zirconolites and calzirtites of 15.66, respectively 15.5 Ma (± 0.1 2σ) and for pyrochlores of 15.35 ± 0.24 Ma. Only the perovskites from the Badberg soevite yielded a U–P concordia age of 14.56 ± 0.86 Ma while the perovskites from bergalites (haüyne melilitites) only gave 206Pb/238U and 208Pb/232Th ages of 15.26 ± 0.21, respectively, 15.28 ± 0.48 Ma. The main Kaiserstuhl rock types were emplaced over a time span of 1.6 Ma almost 1 million years before the carbonatites and carbonate-rich foidites. These were emplaced within only 0.32 Ma.
Tropical forest soils are a significant source for the greenhouse gas N2O as well as for NO, a precursor of tropospheric ozone. However, current estimates are uncertain due to the limited number of field measurements. Furthermore, there is considerable spatial and temporal variability of N2O and NO emissions due to the variation of environmental conditions such as soil properties, vegetation characteristics and meteorology. In this study we used a process-based model (ForestDNDC-tropica) to estimate N2O and NO emissions from tropical highland forest (Nyungwe) soils in southwestern Rwanda. To extend the model inputs to regional scale, ForestDNDC-tropica was linked to an exceptionally large legacy soil dataset. There was agreement between N2O and NO measurements and the model predictions though the ForestDNDC-tropica resulted in considerable lower emissions for few sites. Low similarity was specifically found for acidic soil with high clay content and reduced metals, indicating that chemo-denitrification processes on acidic soils might be under-represented in the current ForestDNDC-tropica model. The results showed that soil bulk density and pH are the most influential factors driving spatial variations in soil N2O and NO emissions for tropical forest soils. The area investigated (1113 km2) was estimated to emit ca. 439 ± 50 t N2O-N yr−1 (2.8–5.5 kg N2O-N ha−1 yr−1) and 244 ± 16 t NO-N yr−1 (0.8–5.1 kg N ha−1 yr−1). Consistent with less detailed studies, we confirm that tropical highland rainforest soils are a major source of atmospheric N2O and NO.
Spatial variations of nitrogen trace gas emissions from tropical mountain forests in Nyungwe, Rwanda
(2012)
Globally, tropical forest soils represent the second largest source of N2O and NO. However, there is still considerable uncertainty on the spatial variability and soil properties controlling N trace gas emission. Therefore, we carried out an incubation experiment with soils from 31 locations in the Nyungwe tropical mountain forest in southwestern Rwanda. All soils were incubated at three different moisture levels (50, 70 and 90 % water filled pore space (WFPS)) at 17 °C. Nitrous oxide emission varied between 4.5 and 400 μg N m−2 h−1, while NO emission varied from 6.6 to 265 μg N m−2 h−1. Mean N2O emission at different moisture levels was 46.5 ± 11.1 (50 %WFPS), 71.7 ± 11.5 (70 %WFPS) and 98.8 ± 16.4 (90 %WFPS) μg N m−2 h−1, while mean NO emission was 69.3 ± 9.3 (50 %WFPS), 47.1 ± 5.8 (70 %WFPS) and 36.1 ± 4.2 (90 %WFPS) μg N m−2 h−1. The latter suggests that climate (i.e. dry vs. wet season) controls N2O and NO emissions. Positive correlations with soil carbon and nitrogen indicate a biological control over N2O and NO production. But interestingly N2O and NO emissions also showed a positive correlation with free iron and a negative correlation with soil pH (only N2O). The latter suggest that chemo-denitrification might, at least for N2O, be an important production pathway. In conclusion improved understanding and process based modeling of N trace gas emission from tropical forests will benefit from spatially explicit trace gas emission estimates linked to basic soil property data and differentiating between biological and chemical pathways for N trace gas formation.
Globally, tropical forest soils represent the second largest source of N2O and NO. However, there is still considerable uncertainty on the spatial variability and soil properties controlling N trace gas emission. To investigate how soil properties affect N2O and NO emission, we carried out an incubation experiment with soils from 31 locations in the Nyungwe tropical mountain forest in southwestern Rwanda. All soils were incubated at three different moisture levels (50, 70 and 90% water filled pore space (WFPS)) at 17 °C. Nitrous oxide emission varied between 4.5 and 400 μg N m−2 h−1, while NO emission varied from 6.6 to 265 μg N m−2 h−1. Mean N2O emission at different moisture levels was 46.5 ± 11.1 (50% WFPS), 71.7 ± 11.5 (70% WFPS) and 98.8 ± 16.4 (90% WFPS) μg N m−2 h−1, while mean NO emission was 69.3 ± 9.3 (50% WFPS), 47.1 ± 5.8 (70% WFPS) and 36.1 ± 4.2 (90% WFPS) μg N m−2 h−1. The latter suggests that climate (i.e. dry vs. wet season) controls N2O and NO emissions. Positive correlations with soil carbon and nitrogen indicate a biological control over N2O and NO production. But interestingly N2O and NO emissions also showed a negative correlation (only N2O) with soil pH and a positive correlation with free iron. The latter suggest that chemo-denitrification might, at least for N2O, be an important production pathway. In conclusion improved understanding and process based modeling of N trace gas emission from tropical forests will not only benefit from better spatial explicit trace gas emission and basic soil property monitoring, but also by differentiating between biological and chemical pathways for N trace gas formation.
The future physiology of marine phytoplankton will be impacted by a range of changes in global ocean conditions, including salinity regimes that vary spatially and on a range of short- to geological timescales. Coccolithophores have global ecological and biogeochemical significance as the most important calcifying marine phytoplankton group. Previous research has shown that the morphology of their exoskeletal calcified plates (coccoliths) responds to changing salinity in the most abundant coccolithophore species, Emiliania huxleyi. However, the extent to which these responses may be strain-specific is not well established. Here we investigated the growth response of six strains of E. huxleyi under low (ca. 25) and high (ca. 45) salinity batch culture conditions and found substantial variability in the magnitude and direction of response to salinity change across strains. Growth rates declined under low and high salinity conditions in four of the six strains but increased under both low and high salinity in strain RCC1232 and were higher under low salinity and lower under high salinity in strain PLYB11. When detailed changes in coccolith and coccosphere size were quantified in two of these strains that were isolated from contrasting salinity regimes (coastal Norwegian low salinity of ca. 30 and Mediterranean high salinity of ca. 37), the Norwegian strain showed an average 26% larger mean coccolith size at high salinities compared to low salinities. In contrast, coccolith size in the Mediterranean strain showed a smaller size trend (11% increase) but severely impeded coccolith formation in the low salinity treatment. Coccosphere size similarly increased with salinity in the Norwegian strain but this trend was not observed in the Mediterranean strain. Coccolith size changes with salinity compiled for other strains also show variability, strongly suggesting that the effect of salinity change on coccolithophore morphology is likely to be strain specific. We propose that physiological adaptation to local conditions, in particular strategies for plasticity under stress, has an important role in determining ecotype responses to salinity.
The calcareous substrate of spring-fed fens makes them unique islands of biodiversity, hosting endangered, vulnerable, and protected vascular plants. Hence, spring-fed fens ecosystems require special conservation attention because many of them are destroyed (e.g. drained, forested) and it is extremely difficult or even impossible to restore the unique hydrogeological and geochemical conditions enabling their function. The long-term perspective of paleoecological studies allows indication of former wetland ecosystem states and provides understanding of their development over millennia. To examine the late Holocene dynamics of a calcareous spring-fed fen (Raganu Mire) ecosystem on the Baltic Sea coast (Latvia) in relation to environmental changes, substrate and human activity, we have undertaken high-resolution analyses of plant macrofossils, pollen, mollusc, stable carbon (δ13C) and oxygen (δ18O) isotopes combined with radiocarbon dating (AMS) in three coring locations. Our study revealed that peat deposits began accumulating ca. 7000 cal. yr BP and calcareous deposits (tufa) from 1450 cal. yr BP, coinciding with regional hydrological changes. Several fire events occurred between 4000 and 1600 cal. yr BP, which appeared to have had a limited effect on local vegetation. The most significant changes in the forest and peatland ecosystems were at 3200 cal. yr BP associated with a dry climate stage and high fire activity, and then between 1400 and 500 cal. yr BP potentially associated with temperature changes during the Medieval Climate Anomaly (MCA) and Little Ice Age. Hydrological disturbances in the peatland catchment from 1400 cal. yr BP were most likely strengthened by human activity (deforestation) in this region. The relationship between the development of this peatland and changes in its catchment area, such as land cover changes or fluctuations in groundwater levels, suggest that protection and restoration of spring-fed fen ecosystems should also include the surrounding catchment. The presence of calcareous sediments, as well as appropriate temperature and local hydrological conditions appear to be the most crucial factors controlling Cladium marisus populations in our site - currently at the eastern limit of its distribution in Europe.
Zusammenfassung der Ergebnisse.
1. Eine einheitliche Gliederung der diluvialen Terrassen ist Voraussetzung für die vorliegende Untersuchung.
a) Die Bezeichnung "Mittelterrassen" wurde vermieden, vielmehr ist in Hoch- und Talwegterrasse gegliedert worden. b) Die Höhenbezeichnungen wurden durch Altersbestimmungen ersetzt.
2. Eine gemeinsame Behandlung erforderten die älteren Terrassen des Eis- und Eckbaches.
a) Der Oberlauf des Eckbaches ist tektonisch angelegt. In diesem Engtal wie auch in den südlich folgenden fehlen nicht nur die älteren sondern überhaupt jegliche Terrassen.
b) Die Schotterfluren innerhalb der Marnheimer Bucht stellen Gleithänge dar, an denen der Eisbach nach dem Innern hin heruntergerutscht ist.
c) Schon im Pliozän ist die Scholle der Marnheimer Bucht gegen den Rheintalgraben aufgerichtet.
3. Die Hochterrasse ist nur im nördlichen Gebietsteil ausgebildet, im Süden wird sie durch die Ablagerung der Freinsheimer Tonschichten lokal ersetzt.
4. Die Freinsheimer Tonschichten stellen eine lokale prärißeiszeitliche Auffüllung des rückgesunkenen Mitteldiluvialen Senkungsfeldes dar.
5. Die mittel diluviale Reakkumulation ist eine der bedeutendsten Erscheinungen für die Morphologie des Mainzer Beckens.
a) Infolge der starken Niveaudifferenzen am Rand des Pfälzerwaldes mußte die Aufschüttung gerade hier sehr mächtig sein.
b) Die Schuttkegel sind teils ein Ergebnis dieser Aufschüttung teils ein Ergebnis der flächenhaften Abtragung und mechanischen Zertrümmerung am Gebirgsrand.
c) Morphologische Tatsachen beweisen, daß die südlichen Seitenfliisse des Rheins jünger sind als Pfrimm und Eisbach.
6. Die Ursache für die Entstehung des einzelnen Fluß terrassenrestes im Gebirge (Rotliegendausräumung von Lambrecht-Grevenhausen) ist die Stauung des Speyerbaches unmittelbar vor der Verwerfung Albersweiler-Lindenberg-Bad Dürkheim.
7. Der Niederterrasse kommt im südlichen Teil des Untersuchungsgebietes größere morphologische Bedeutung zu als im nördlichen.
8. Der Südwestteil des Mainzer Beckens kann in einzelne tektonische Senkungsfelder eingeteilt werden, die durch· Verwerfungen begrenzt sind.
a) Erst im Mitteldiluvium sind die Hauptschollen des Rheinhessischen Blockgebirges aus dem allgemeinen Senkungsbereich ausgegliedert worden.
b) Verschiedene morphologische Tatsachen, besonders in der Rheinpfalz, sprechen dafür, daß im Rheintalgraben gegensätzliche Bewegungsrichtungen der sich senkenden Schollen geherrscht haben.
c) Im Mitteldiluvium wirkte noch die alte Bewegungstendenz mit größter Intensität im Innern.
d) Frühestens im Riß-Würm-Interglazial sank alsdann das Mitteldiluviale Senkungsfeld gebirgswärts zurück.
e) Aber auch in gleichen Zeitabschnitten herrschten im Rheintal verschiedene Bewegungsrichtungen, wobei sich Wilsers Ansicht bestätigt, daß das Rheintal in quer gerichtete Unterabschnitte zu gliedern ist, die als Einheiten verschiedensinnige Bewegungen zeigen.
This work analyses several granitic bodies of the Variscan Orogen of Central and Western Europe in order to improve our knowledge about different aspects of their evolution, regarding their ascent and emplacement mechanisms, as well as their deformation history. In the Iberian Massif two granitoid bodies, namely the La Bazana pluton and the Nisa-Alburquerque batholith, were studied in order to decipher their ascent and emplacement history. The La Bazana pluton is a small, sub-circular body in map view that intruded into rocks of the Ossa-Morena Zone in the core of a late upright antiform. Its three-dimensional drop-pipe shape, its internal dome foliation pattern and the structure of the host rock suggest that the magma ascended and emplaced diapirically. The Nisa-Alburquerque batholith is a large body that intruded into rocks of the Central Iberian Zone, the Central Unit, and the Ossa-Morena Zone. Its cartographic shape is elongate and parallel to the NW—SE to WNW—ESE Variscan structures. In the light of the available structural data and the gravimetric models, the intrusion is viewed as a continuous lateral magma flow from the eastern root guided towards the west through the southern limb of a kilometre-scale antiform. As mass-transfer mechanisms, a combination of rigid translation of the country rocks, stoping, and possibly ballooning is proposed. In the Bohemian Massif several small granitoid bodies showing a strong solid-state deformation were studied in order to integrate their tectonometamorphic history in the geotectonic framework of the south-western Bohemian Massif, focusing principally on the deformation phase referred to as D3. Four ductile deformation phases are proposed for the study area. D1 produced high-temperature fabrics under upper amphibolite to granulite facies conditions. Its kinematics is unknown. D2 occurred under amphibolite to upper greenschist facies conditions under N—S to NNW—SSE compression. It is responsible for a subvertical NW—SE striking foliation in migmatites developed under dextral simple shear and for the deformation at the Bayerischer Pfahl shear-zone system at its earlier stages. Many granitoid dykes and stocks were found to be affected by sinistral shear along subvertical planes trending ENE to ESE. Since this deformation, which is called D3 in the present work, is not compatible with a N—S to NNW—SSE compression, it is proposed that these sinistral shear zones in granites do not belong to the Bayerischer Pfahl shear-zone system and constitute themselves a separated one, which is called “D3 shear-zone system”. D3 took place under upper greenschist to lower amphibolite facies conditions (~480-550°C). Both the intrusion and the deformation of the granites affected by D3 occurred at deep to intermediate levels of the crust, whereas the deformation took place under NE—SW compression. Datings on two of the deformed granites yielded 324.4 ± 0.8 Ma and 315.0 ± 1.0 Ma: Thus, the age of D3 is most probably ~315 Ma. The intrusion of most of the sheared granitoids was pre-kinematic with respect to D3. After D3 the N—S to NNW—SSE compression which governed D2 was restored, giving way to the next deformation phase D4, which was linked to further deformation at and next to the principal shears of the Bayerischer Pfahl shear-zone system under greenschist facies conditions. The causes for the change of the stress field leading to a NE—SW compression during D3 might be related to (1) global changes in the dynamics of the tectonic plates in late Variscan times, (2) orogenic collapse leading to the sinking of the Teplá-Barrandian and lateral extrusion of the surrounding Moldanubian rocks, (3) distortion of the regional stress field by local intrusion of large stocks, such as the Saldenburg granite of the Fürstenstein Massif, or (4) distortion of the regional stress field due to the existence of ephemeral releasing bends in the Bayerischer Pfahl shear zone during its early evolution.
The crude oil constituents benzene, toluene, ethylbenzene, and the three xylene isomers (BTEX) are the dominating groundwater contaminants originating from surface spill accidents by oil production facilities and with gasoline and jet fuel. Thereby BTEX posing a threat to the world´s scarce drinking water resources due to their water solubility and toxicity. An active remediation cleanup involving a BTEX event proves not only to be very expensive but almost impossible when it comes to the complete removal of contaminants from the subsurface. A favoured and common practice is combining an active remediation process focussing on the source of contamination coupled together with the monitoring of the residual contamination in the subsurface (monitored natural attenuation; MNA). MNA include all naturally occuring biological, chemical and physical processes in the subsurface. The general goal of this work was to improve the knowledge of biodegradation of aromatic hydrocarbons under anaerobic conditions in groundwater. For this groundwater and soil at the former military underground storage tank (UST) site Schäferhof – Süd near Nienburg/Weser (Niedersachsen, Germany) were sampled and analysed. The investigations were done in collaboration of the Umweltbundesamt, the universitys of Frankfurt and Bremen and the alphacon GmbH Ganderkesee. To investigate the extent of groundwater contamination, the terminal electron acceptor processes (TEAPs) and the metabolites of BTEX degradation in groundwater, six observation wells were sampled at regular intervals between January 2002 and September 2004. The wells were positioned in order to cover the upstream, the source area and the downstream of the presumed contamination source. Additionally, vertical sediment profiles were sampled and investigated with respect to spreading and concentration of BTEX in the subsurface. A large residual contamination involving BTEX is present in soil and groundwater at the studied locality. Maximum BTEX concentration values of 17 mg/kg were recorded in analysing sediment in the unsaturated zone. In the capillary fringe, values of 450 mg/kg were recorded (October 2004) and in the saturated zone maximum values of 6.7 mg/kg BTEX were detected. The groundwater samples indicate increasing BTEX concentrations in the groundwater flow direction (from 532 µg/l up to 3300 µg/l (mean values)). Biodegradation of aromatic hydrocarbons under anaerobic conditions in the sub surface at contaminated sites is characterised by generation of metabolites. From the monoaromatic hydrocarbons BTEX metabolites such as benzoic acid (BA) and the methylated homologs and C1-and C2-benzyl-succinic acids (BSA) are generated as intermediates. A solid-phase extraction method based on octadecyl-bonded silica sorbent has been developed to concentrate such metabolite compounds from water samples followed by derivatization and gas chromatography/mass spectrometry (GC/MS) of the extracts. The recovery rate range between 75 and 97%. The method detection limit was 0.8 µg/l. Organic acids were identified as metabolic by-products of biodegradation. Benzoic acid, C1-, C2- and C3-benzoic acid were determined in all contaminated wells with considerable concentrations. Furthermore, the depletion of the dominant terminal electron acceptors (TEAs) oxygen, nitrate, and sulphate and the production of dissolved ferrous iron and methane in groundwater indicate biological mediated processes in the plume evidently proving the occurrence of NA. A large overlap of different redox zones at the studied part of the plume has been observed. A important finding in this study is the strong influence of groundwater level fluctuations on the BTEX concentration in groundwater. A very dry summer in 2003 was recorded during the monitoring period, resulting on site in a drop of the groundwater level to 1.7 m and a concomitant increase of BTEX concentrations from 240 µg/l to 1300 µg/l. The groundwater level fluctuations, natural degradation and retention processes essentially influence BTEX concentrations in the groundwater. Groundwater level fluctuations have by far a stronger influence than the influence of biological degradation. Increasing BTEX concentrations are hence not a consequence of limited biological degradation. Another part of the study was to observe the isotopic fractionation of the electron acceptor Fe(III), due to biologically mediated reduction of Fe(III) to the watersoluble Fe(II) at the site and first field data are presented. Both groundwater and sediment samples were analysed with respect to their Fe isotopic compositions using high mass resolution Multi Collector-Inductively Coupled Plasma-Mass Spectrometry (MC-ICP-MS). The delta56Fe -values of groundwater samples taken from observation wells located downstream of the source area were isotopically lighter than delta56Fe -values obtained from groundwater in the uncontaminated well. The Fe isotopic composition of most parts of the sediment profile was similar to the Fe isotopic composition of uncontaminated groundwater. Thus, a significant iron isotope fractionation can be observed between sediment and groundwater downstream of the BTEX contamination.
Diamonds growing in the Earth’s mantle often trap inclusions of fluids that are highly saline in composition. These fluids are thought to emerge from deep in subduction zones and may also be involved in the generation of some of the kimberlite magmas. However, the source of these fluids and the mechanism of their transport into the mantle lithosphere are unresolved. Here, we present experimental results showing that alkali chlorides are stable solid phases in the mantle lithosphere below 110 km. These alkali chlorides are formed by the reaction of subducted marine sediments with peridotite and show identical K/Na ratios to fluid inclusions in diamond. At temperatures >1100°C and low pressures, the chlorides are unstable; here, potassium is accommodated in mica and melt. The reaction of subducted sediments with peridotite explains the occurrence of Mg carbonates and the highly saline fluids found in diamonds and in chlorine-enriched kimberlite magmas.
Sedimentbilanzen haben sich als Methode zur Quantifizierung von Sedimentflüssen in Raum und Zeit in den Geowissenschaften etabliert. Sie eröffnen die Möglichkeit, differenzierte Aus¬sagen über die Erosions- und Sedimentationsdynamik von Einzugsgebieten zu treffen. Ziel der vorliegenden Arbeit ist es, die holozäne Erosions- und Sedimentationsentwicklung im mesoskaligen Mittelgebirgseinzugsgebiet des Speyerbachs im Pfälzerwald zu erfassen, und räumlich und zeitlich möglichst differenziert darzulegen. Um Langzeit-Sedimentbilanzen für den Speyerbach zu berechnen wurden verfügbare Daten zum Boden, eine eigene Kartierung der Erosion und Sedimentation sowie eine intensive (OSL und 14C-) Datierung zweier Stand¬orte durchgeführt. Die Sedimente wurden durch eine direkte Kartierung erfasst. Die Erosions¬tiefe errechnet sich aus der Subtraktion der aktuellen Mächtigkeit der Hauptlagen und der Parabraunerden vom initialen Zustand (= Berechnungsgrundlage).
Die Sedimentbilanz I basiert auf öffentlich zugänglichen bodenkundlichen Punkt- und Flächendaten und hat eine Erosion von ~27 Mio. m³ mit einem Einzugsgebiets-Sedimentaus¬tragsverhältnis (CSDR) von 31,5 % ergeben. Die Sensitivitätsanalyse belegt eine hohe Abhängigkeit des Ergebnisses von der Wahl der Berechnungsgrundlage. Aufgrund fehlender Daten sind eine höhere räumliche Auflösung sowie Aussagen zur zeitlichen Entwicklung nicht möglich.
Die Berechnung der Sedimentbilanz II erfolgte auf der Grundlage eigens erhobener Punkt- und Flächendaten, womit die Anwendung eines nested approach möglich wurde: Neben der Gesamtbilanz für den Speyerbach (sechste Strahler-Ordnung) wurden Bilanzen für Teilein¬zugsgebiete erster und vierter Strahler-Ordnung erstellt, anhand derer die Skalenabhängigkeit der Sedimentdynamik diskutiert werden konnte. Es wurden ~109 Mio. m³ und ein CSDR von 5 % errechnet und ebenfalls eine hohe Sensitivität gegenüber der Änderung der Erosionstiefen festgestellt.
Die erfolgreiche Datierung von periglazialen Deckschichten zweier Bodenprofile unterstützt die Ergebnisse der Landnutzungsrekonstruktion aus Literaturdaten und historischen Karten und zeigt, dass in den Tälchen erster Ordnung Erosion verstärkt in der Neuzeit stattfand. Nur in den lösslehmbeeinflussten Gebieten hat sich die Besiedlung im Frühmittelalter in der Ablagerung von Bodensedimenten abgebildet. Es wurden frühholozäne Umlagerungsprozesse am Hang identifiziert. Aufgrund der guten Datierungseigenschaften der sandigen periglazia¬len Lagen wäre das Untersuchungsgebiet geeignet, der Frage nach der Parallelisierung der frühholozänen Umlagerungen von Hangsedimenten mit Klimaschwankungen nachzugehen.
Die vorliegende Arbeit liefert mit den erstellten Sedimentbilanzen und der Darlegung der Landnutzungsverhältnisse ein regionales Beispiel für Mittelgebirgsräume im Rhein-Einzugs¬gebiet. Die mikro- bis mesoskaligen Ergebnisse folgen der generellen Tendenz anderer welt¬weiter Studien, wonach die Sedimentaustragsverhältnisse mit steigender Einzugsgebietsgröße abnehmen. Die Werte der Sedimentbilanz II liegen jedoch deutlich unter denen der Lössge¬biete und belegen, dass sich die Zwischenspeicherung in der Mittelgebirgsregion höher ist. Die räumliche Differenzierung zeigt regionale Unterschiede, die auf der Zugänglichkeit, der administrativen Zugehörigkeit und die naturräumliche Ausstattung zurückzuführen sind. Arbeiten in anderen Sandsteinregionen Deutschlands sind derzeit im Gange und werden in Zukunft eine Einschätzung der vorliegenden Untersuchung zulassen.
Strain localization in the lithosphere and the formation, evolution, and maintenance of resulting plate boundaries play a crucial role in plate tectonics and thermo‐chemical mantle convection. Previously activated lithospheric deformation zones often appear to maintain a “memory” of weakening, leading to tectonic inheritance within plate reorganizations including the Wilson cycle. Different mechanisms have been proposed to explain such strain localization, but it remains unclear which operates on what spatio‐temporal scales, and how to best incorporate them in large‐scale mantle convection models. Here, we analyze two candidates, (1), grain‐size sensitive rheology and, (2), damage‐style parameterizations of yield, stress which are sometimes used to approximate the former. Grain‐size reduction due to dynamic recrystallization can drive localization in the ductile domain, and grain growth provides a time‐dependent rheological hardening component potentially enabling the preservation of rheological heterogeneities. We compare the dynamic weakening and hardening effects as well as the timescales of strength evolution for a composite rheology including grain‐size dynamics with a pseudo‐plastic rheology including damage‐ (or “strain”‐) dependent weakening. We explore the implications of different proposed grain‐size evolution laws, and test to which extent strain‐dependent rheologies can mimic the weakening and hardening effects of the more complex micro‐physical behavior. Such an analysis helps to better understand the parallels and differences between various strain‐localization modeling approaches used in different tectonics and geodynamics communities. More importantly, our results contribute to efforts to identify the key ingredients of strain‐localization and damage hysteresis within plate tectonics and how to represent those in planetary‐scale modeling.
In der Monte Cavallo-Gruppe fand Verf. in Stauseesedimenten fossile Holzstücke, für die die 14 C-Datierung ein Alter von 29 350 ± 460 Jahren vor 1950 n. Chr. ergab. Die schluffigen Ablagerungen, die in etwa 900 m, fast 80 m über dem heutigen Flußbett des T. Caltea aufgeschlossen sind, ruhen auf Schottern und werden von Moräne überlagert.
Aufgrund seiner stratigraphischen Lage und seines 14C-datierten Alters kann das Holz (Picea abies bzw. Larix) einem zeitlichen Äquivalent des Paudorf-Interstadials zugeordnet werden. Dieser Fund von Großresten ermöglicht somit eine erste absolute Datierung des Paudorf-Interstadials für die Südalpen und Oberitalien.
Innerhalb einer Stadt bildet sich durch die dichte Bebauung und den erhöhten Energieumsatz gegenüber dem Umland ein davon deutlich abweichendes "Stadtklima" aus. Dieses ist beispielsweise durch eine höhere Temperatur in der Stadt gekennzeichnet, welche zur Ausbildung der sogenannten städtischen Wärmeinsel führt. Zudem lassen regionale Klimamodelle für die nächsten Jahrzehnte Klimaänderungen erwarten, die sich in den städtischen Ballungsräumen durch die Überlagerung mit der städtischen Wärmeinsel deutlich belastender auswirken als im Umland. Dies ist für die Menschen von elementarem Interesse, da bereits heute mehr als die Hälfte der Weltbevölkerung in Städten lebt. Der Klimawandel findet bereits statt: 60-jährige Messungen des Deutschen Wetterdienstes am Flughafen Frankfurt/Main belegen einen signifikanten Anstieg des Jahresmittels der Lufttemperatur von 0,35 °C pro Dekade. Die Anzahl der mittleren jährlichen Sommertage, das sind Tage an denen die Lufttemperatur 25 °C erreicht oder überschreitet, weist ebenfalls einen signifikanten Trend von 4,3 Tagen pro Dekade auf. Wenn dieser beobachtete Trend unverändert weiterginge, so wären für die Klimaperiode 2021 - 2050 durchschnittlich etwa 21 Sommertage pro Jahr mehr als in der Klimaperiode 1971 - 2000 zu erwarten. Eine zuverlässige Abschätzung muss jedoch die erwartete Änderung klimarelevanter Spurenstoffe berücksichtigen und daher auf den verfügbaren globalen und regionalen Klimaprojektionen basieren. Ziel der Untersuchung war es deshalb, auf der Basis von Projektionen regionaler Klimamodelle die Auswirkungen des Klimawandels für detaillierte Stadtstrukturen aufzuzeigen. Mit Hilfe eines Stadtklimamodells und der am Beispiel Frankfurt/Main entwickelten sogenannten „Quadermethode“ (Früh et al., 2011) konnte erstmals sowohl die vergangene als auch die zukünftige Wärmebelastung für Frankfurt am Main unter Berücksichtigung der vielfältigen Bebauungsstrukturen und sonstiger Flächennutzungen simuliert werden. Auch die klimatischen Auswirkungen der größeren Planungsvorhaben der Stadt wurden in diesem Zusammenhang untersucht. Auf der Grundlage des moderaten IPCC Emissionsszenarios A1B ergibt sich für das Stadtgebiet von Frankfurt bis zum Jahr 2050 eine Zunahme der mittleren jährlichen Anzahl von Sommertagen von derzeit etwa 44 Tagen pro Jahr, um weitere 5 bis 31 Tage. Damit wird Mitte des Jahrhunderts im Sommerhalbjahr jeder zweite bis vierte Tag in Frankfurt wärmer als 25 °C sein. Gleichzeitig wird auch die mittlere jährliche Anzahl "Sommerabende", das sind Abende an denen es um 22 Uhr noch mindestens 20 °C warm ist, um 5 bis 33 Tage ansteigen. Auch die Anzahl der "heißen Tage" mit einer Höchsttemperatur von mindestens 30 °C und der Tropennächte mit Lufttemperaturen, die nicht unter 20 °C sinken, wird deutlich zunehmen. Aufgrund der heute noch geringen Anzahl solcher Tage lassen sich für die Zukunft derzeit keine verlässlichen Aussagen treffen. Dies gilt auch für alle Untersuchungen, die für die Klimaperiode 2071 - 2100 durchgeführt wurden. Die Studie zeigt, dass die Zunahme der Sommertage bis Mitte des Jahrhunderts sich nicht signifikant zwischen dicht und locker bebauten Stadtteilen unterscheidet. Die Wärmebelastung wird also gleichermaßen stark zunehmen und zukünftig auch dort am höchsten sein wo sie es heute schon ist. Die Unterschiede zwischen Stadt und Umland werden sich aber nicht wie befürchtet verschärfen. Aber die Wahrscheinlichkeit, dass Hitzesommer – wie beispielsweise im Jahr 2003 – häufiger auftreten werden, nimmt bis Mitte des Jahrhunderts zu. Betrachtet man unterschiedliche Bebauungsstrukturen in Frankfurt, so belegen die Modellergebnisse zusätzlich, dass in dicht bebauten Gebieten, wie zum Beispiel der Innenstadt, die Wärmebelastung mit bis zu 54 Sommertagen pro Jahr bereits heute am stärksten ist. Hochhäuser, wie im Frankfurter Bankenviertel, können den Effekt dichter Bebauung zwar durch ihre abschattende Wirkung zumindest tagsüber etwas mildern. Da allerdings der Effekt der nächtlichen Wärmeinsel durch die Hochhäuser verstärkt wird, ist keineswegs als Anpassungsmaßnahme auf den Hochhausbau zu setzen. Neben den Auswirkungen der regionalen Klimaänderungen auf die Stadt werden auch die Auswirkungen bereits geplanter Veränderungen der Stadt untersucht. Dabei kann gezeigt werden, dass eine Umwandlung von bebauten Flächen in Grünflächen die durch den Klimawandel erwartete Zunahme an Sommertagen und -abenden etwa halbieren würde. Umgekehrt kann eine Verdichtung der Bebauung die erwartete Zunahme an Sommertagen und -abenden nahezu verdoppeln. Die Auswirkungen solcher Maßnahmen werden aber lokal sehr begrenzt sein. Um der erwarteten regionalen Klimaerwärmung im gesamten Stadtgebiet gegenzusteuern ist daher eine klimagünstige Gestaltung der Stadt in möglichst vielen Stadtbereichen notwendig. Parks und Grünanlagen nehmen unter zukünftigen Klimabedingungen somit in ihrer Bedeutung stark zu.
In der vorliegenden Arbeit wurde ein neuer optischer Aufbau für das Laserlabor der Abteilung Kristallographie im FB 11 an der Goethe-Universität Frankfurt beschrieben. Mit Hilfe dieses Aufbaus konnten verschiedene spektroskopische Methoden genutzt werden, um die - von Druck und Temperatur abhängige - Phasenstabilität von Calcium- und Eisencarbonaten zu untersuchen. Mit Hilfe von Raman-Spektroskopie konnte das Phasendiagramm von Calciumcarbonat (CaCO3) teilweise neu bestimmt werden. Fluoreszenzuntersuchungen an dotierten CaCO3 Proben ergaben, dass sich Europium-dotierter Calcit zunächst in eine amorphe Form umwandelt, bevor er bei ca. 15 GPa in eine amorphe 'aragonitische' Form umgewandelt wird. Die Umwandlung ist nicht reversibel. Laserheizexperimente bei 18.5 GPa an dotiertem Siderit (FeCO3) führten zur Bildung eines neuen Hochdruck-Hochtemperatur FeCO3 -Polymorphs. Die Strukturlösung erfolgte mit Hilfe von Röntgendaten, die am Deutschen Elektronen-Synchrotron (DESY) in Hamburg gewonnen wurden. Schließlich wurde eine neue Methode zur Bestimmung von Temperaturen in Laserheizexperimenten beschrieben. Sie beruht auf der Abschwächung eines Fluoreszenzsignals durch die Temperatur, welche durch die Wechselwirkung eines Heizlasers mit der Probe erzeugt wird.
Im Vordergrund dieser Dissertation steht die Methode der Mikromorphologie, die verknüpft mit weiteren bodenkundlichen Analysen sowohl bodenkundliche Fragen, als auch siedlungsfunktionale Fragen beantworten kann. Die Methode dient also ideal der Verknüpfung von Bodenkunde und Archäologie. Der Begriff Archäopedologie beschreibt genau diese Verknüpfung – die Anwendung bodenkundlicher Methoden zur Bearbeitung archäologischer Fragestellungen. Inhalt des ersten Themenschwerpunktes dieser Arbeit ist der Vergleich von Böden und Sedimenten des Tells Chuera und seiner Umgebung. Ziel war es, die Böden hinsichtlich verschiedener Ausgangssubstrate, unterschiedlicher Entwicklungsdauer und Reliefpositionen miteinander zu vergleichen. Es konnte nachgewiesen werden, dass die Böden des Untersuchungsgebietes sich in Bezug auf ihre unterschiedlichen Substrate unterscheiden lassen. Auf den natürlichen Substraten des Waditals, den Hochflutsedimenten des Wadis Chuera, können ausschließlich haplic Calcisols ausgewiesen werden. Diese Böden sind durch einen Kalkanreicherungshorizont im Unterboden gekennzeichnet. In den anthropogen beeinflussten Substraten des Tells können ebenso vornehmlich Calcisols beschrieben werden. Diesen Böden wird ein technic vorangestellt, da sie sich in technogenen Substraten, wie z.B. Lehmziegelmaterial entwickelt haben. Geht der auf dem Tell als Konstruktionsmaterial verwendete Gips in die Bodengenese ein, werden Gypsisols gebildet. In allen untersuchten Böden sind dieselben pedogenen Prozesse wirksam: Bioturbation, Kalktranslokation und Gefügebildung. Eine Unterscheidung hinsichtlich ihrer Entwicklungszeiträume kann nicht getroffen werden. Sowohl auf dem Siedlungshügel, auf dem die Bodenentwicklung in dem Siedlungshiatus von 600 Jahren und nach der Aufgabe der Siedlung untersucht werden konnte, wie auch in der Umgebung, laufen unabhängig vom Zeitfenster dieselben Prozesse ab. Die Böden weisen keine bedeutenden pedogenetischen Unterschiede auf, die gravierende ökologisch-klimatische Veränderungen anzeigen und somit die Aufgabe der Siedlung erklären könnten. Der zweite Teil der Dissertation widmet sich der mikromorphologischen Analyse von Siedlungsresten. Kulturschichten ausgewählter Standorte (Oberstadt, Unterstadt, Straßen, Räume) wurden hinsichtlich ihrer Nutzung untersucht. Anhand von Dünnschliffanalysen konnten innerhalb der beprobten Areale verschiedene Bereiche klar abgegrenzt werden. So deuten Phytolithschichten innerhalb eines Gebäudes auf Pflanzenmatten hin, die typischerweise in Ruhe- oder Essensbereichen als Bodenbelag dienten. Darüber hinaus konnten auch Hinweise auf den Aufenthalt von Tieren in der Siedlung gefunden werden. Dies war durch den Nachweis von Dungresten und zahlreichen fäkalen Sphäruliten, die Schafen oder Ziegen zuzuordnen sind, möglich. Ob die Tiere in direkter Nachbarschaft zu den Menschen lebten, konnte bislang noch nicht geklärt werden. Gesichert ist, dass Tier und Mensch gemeinsam die Straßen und Gassen von Tell Chuera genutzt haben.
Micromorphology is a suitable method to study the contents and stratigraphic relationships of pit fills. Within the ramparts of Corneşti-Iarcuri, fill layers of a pit were sampled. Th e pit fill was macroscopically divided into primary and secondary fill due to striking differences. These differences could be verified and concretized micromorphologically.
The continental expression of global cooling during the Miocene Climate Transition in Central Asia is poorly documented, as the tectonically active setting complicates the correlation of Neogene regional and global climatic developments. This study presents new geochemical data (CaSO4 content, carbonate δ13C and δ18O) from the endorheic alluvial‐lacustrine Aktau succession (Ili Basin, south‐east Kazakhstan) combined with findings from the previously published facies evolution. Time series analysis revealed long‐eccentricity forcing of the paleohydrology throughout the entire succession, split into several facies‐dependent segments. Orbital tuning, constrained by new laser ablation U‐Pb dates and a preexisting magnetostratigraphy, places the succession in a 5.0 Ma long interval in the middle to late Miocene (15.6 to 10.6 Ma). The long‐term water accumulation in the Ili Basin followed the timing of the Miocene Climate Transition, suggesting increased precipitation in the catchment area in response to climate cooling and stronger westerly winds. This was paced by minima of the 2.4 Ma eccentricity cycle, which favored the establishment of a discharge playa (~14.3 Ma) and a perennial lake (12.6 to 11.8 Ma). Furthermore, low obliquity amplitudes (nodes) caused a transient weakening of the westerlies at ~13.7 to 13.5 Ma and at ~12.7 Ma, resulting in negative hydrological budgets and salinization. Flooding of the windward Ili Basin coeval with aridification in the leeward basins suggests that the Tian Shan was a climate boundary already in the middle Miocene. Our results emphasize the impact of climate fluctuations on the westerlies' strength and thus on Central Asian hydrology.