Improved provenance tracing of Asian dust sources using rare earth elements and selected trace elements for palaeomonsoon studies on the eastern Tibetan Plateau   总被引：2，自引：0，他引：2  

Marion Ferrat  Dominik J. Weiss  Stanislav Strekopytov  Hongyun Chen  Youbin Sun  Ryuji Tada 《Geochimica et cosmochimica acta》2011,75(21):6374-6399

The Asian Monsoon forms an important part of the earth’s climate system, yet our understanding of the past interactions between its different sub-systems, the East Asian and Indian monsoons, and between monsoonal winds and other prevailing wind currents such as the Westerly jet, is limited, particularly in central Asia. This in turn affects our ability to develop climate models capable of accurately predicting future changes in atmospheric circulation patterns and monsoon intensities in Asia. Provenance studies of mineral dust deposited in terrestrial settings such as peat bogs can address this problem directly, by offering the possibility to examine past deposition rates and wind direction, and hence reconstruct past atmospheric circulation patterns. However, such studies are challenged by several issues, most importantly the identification of proxies that unambiguously distinguish between the different potential dust sources and that are independent of particle size. In addition, a single analytical method that is suitable for sample preparation of both dust source (i.e. desert sand, soil) and receptor (i.e. dust archive such as peat or soil profiles) material is desirable in order to minimize error propagation derived from the experimental and analytical work. Here, an improved geochemical framework of provenance tracers to study atmospheric circulation patterns and palaeomonsoon variability in central Asia is provided, by combining for the first time mineralogical as well as major and trace elemental (Sc, Y, Th and the rare earth elements) information on Chinese (central Chinese loess plateau, northern Qaidam basin and Taklamakan, Badain Juran and Tengger deserts), Indian (Thar desert) and Tibetan (eastern Qinghai-Tibetan Plateau) dust sources.Quartz, feldspars and clay minerals are the major constituents of all studied sources, with highly variable calcite contents reflected in the CaO concentrations. Chinese and Tibetan dust sources are enriched in middle REE relative to the upper continental crust and average shale but the Thar desert has a REE signature distinctly different from all other dust sources. There are significant differences in major, trace and REE compositions between the coarse and fine fractions of the surface sands, with the finest <4 μm fraction enriched in Al₂O₃, Fe₂O₃, MnO, MgO and K₂O and the <32 μm fractions in Sc, Y, Th and the REE relative to the coarse fractions. The <4 μm fraction best represents the bulk REE geochemistry of the samples. The provenance tracers Y/∑REE, La/Er, La/Gd, Gd/Er, La/Yb, Y/Tb, Y/La, Y/Nd and to a certain extent the europium anomaly Eu/Eu^∗ (all REE normalized to post-Archean Australian shale, PAAS) are particle size-independent tracers, of which combinations of Y/∑REE, La/Yb, Y/Tb, Y/La and Eu/Eu^∗ can be used to distinguish the Thar desert, the Chinese deserts, the Chinese loess plateau and the Tibetan soils. Their independence upon grain size means that these tracers can be applied to the long-range provenance tracing of Asian dust even when only bulk samples are available in the source region. Combinations of La/Th, Y/Tb, Y/∑REE, Sc/La and Y/Er distinguish the Tibetan soils from the Chinese loess plateau and the Chinese deserts. La/Th and notably Th/∑REE isolate the signature of the Badain Juran desert and the combination of Sc/La and Y/Er that of the Taklamakan desert. The similarity in all trace and REE-based provenance tracers between the northern Qaidam basin and Tengger desert suggests that these two deposits may have a common aeolian source.  相似文献   

Lacustrine sediments and lichen transplants: two contrasting and complimentary environmental archives of natural and anthropogenic lead in the South Urals, Russia     

Baruch Spiro  Valery Udachin  Ben J. Williamson  O. William Purvis  Svetlana G. Tessalina  Dominik J. Weiss 《Aquatic Sciences - Research Across Boundaries》2013,75(2):185-198

Lead (Pb) concentrations and isotope ratios of two different geochemical archives are compared; lake sediment cores and lichens (Hypogymnia physodes, naturally growing and transplanted) from a ca. 80 km-long transect centred on the Cu smelter and former mining town of Karabash, Ural Mountains, Russia. Lead concentrations in sediment cores from 10 lakes were generally low near their base and show an abrupt increase in their upper portions interpreted to coincide with the onset of large-scale smelting operations in 1910. Lead isotope ratios derived from ²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb, ²⁰⁸Pb of the bottom layers differed significantly from those of the top. The top sediments have isotope ratios that show distinct end members, one of which was the stack dust from the Karabash smelter, which is similar to the Pb derived from ores from Sibay, a major mine in the Urals. The composition of the bottom sediment layers generally fall slightly off a mixing line between the top sediments and average Earth’s upper crust. Lichens transplanted from a reference site, as well as naturally growing lichens, sampled from southwest of the smelter have isotope ratios similar to those of the stack dust. Lichens to the northeast contained Pb from the smelter, but are increasingly influenced by other sources probably leaded petrol and local soils, and a signature derived from a source enriched in ²⁰⁷Pb. Vegetables collected from local kitchen gardens contained Pb from an additional atmospheric source, possibly coal. Our work confirms that: (1) Pb isotopes in lake sediments provide a long-term record of inputs and allows the characterisation of natural and anthropogenic sources; (2) Pb isotopes in lichens provide a short-term record of local and long-range atmospheric deposition at high spatial resolution and short time scales as they replace their Pb content within a few months; (3) determination of all four stable Pb isotopes is necessary for the identification of the sources of Pb and is extremely sensitive for discerning minor source signatures, even in an area with a dominant source such as a smelter. Particularly significant for the Karabash area is that ore-smelter-derived airborne Pb is a major component in the lake sediments and lichens but its contribution reaches insignificant levels ca. 40 km from the smelter.  相似文献   

Deglaciation history of Lake Ladoga (northwestern Russia) based on varved sediments     

Raphael Gromig  Bernd Wagner  Volker Wennrich  Grigory Fedorov  Larisa Savelieva  Elodie  Lebas  Sebastian Krastel  Dominik Brill  Andrei Andreev  Dmitry Subetto  Martin Melles 《Boreas: An International Journal of Quaternary Research》2019,48(2):330-348

Lake Ladoga in northwestern Russia is Europe's largest lake. The postglacial history of the Ladoga basin is for the first time documented continuously with high temporal resolution in the upper 13.3 m of a sediment core (Co1309) from the northwestern part of the lake. We applied a multiproxy approach including radiographic imaging, (bio‐)geochemical and granulometric analyses. Age control was established combining radiocarbon dating with varve chronology, the latter anchored to a correlated radiocarbon age from a lake close by. The age‐depth model reveals the onset of glacial varve sedimentation at 13 910±140 cal. a BP, when Lake Ladoga was part of the Baltic Ice Lake. Linear extrapolation of published retreat rates of the Scandinavian Ice Sheet provides a formation age of the Luga moraine close to Lake Ladoga's southern shore of 14.5–15.9 cal. ka BP, older than previously assumed. Varve sedimentation covers the Bølling/Allerød interstadial, the Younger Dryas stadial and the Early Holocene. Varve‐thickness variations, conjoined with grain‐size and geochemical variations, inform about the relative position of the Scandinavian Ice Sheet and the climate during the deglaciation phase. The upper limit of the varved succession marks the change from glaciolacustrine to normal lacustrine sedimentation and post‐dates the drainage of the Baltic Ice Lake as well as the formation of the Salpausselkä II moraine north of Lake Ladoga, by c. 250 years. The Holocene sediment record is divided into three periods in the following order: (i) a lower transition zone between the Holocene boundary and c. 9.5 cal. ka BP, characterized by mostly massive sediments with low organic content, (ii) a phase with increased organic content from c. 9.5 to 4.5 cal. ka BP corresponding to the Holocene Thermal Maximum, and (iii) a phase with relatively stable sedimentation in a lacustrine environment from c. 4.5 cal. ka BP until present.  相似文献   

Deterministic earthquake damage and loss assessment for the city of Bucharest, Romania   总被引：1，自引：0，他引：1  

Dominik Lang  Sergio Molina-Palacios  Conrad Lindholm  Stefan Balan 《Journal of Seismology》2012,16(1):67-88

On March 4, 1977, an earthquake with a moment magnitude M _w 7.4 at a hypocentral depth of 94 km hit the Vrancea region (Romania). In Bucharest alone, the earthquake caused severe damage to 33,000 buildings while 1,424 people were killed. Under the umbrella of the SAFER project, the city of Bucharest, being one of the larger European cities at risk, was chosen as a test bed for the estimation of damage and connected losses in case of a future large magnitude earthquake in the Vrancea area. For the conduct of these purely deterministic damage and loss computations, the open-source software SELENA is applied. In order to represent a large event in the Vrancea region, a set of deterministic scenarios were defined by combining ranges of focal parameters, i.e., magnitude, focal depth, and epicentral location. Ground motion values are computed by consideration of different ground motion prediction equations that are believed to represent earthquake attenuation effects in the region. Variations in damage and loss estimates are investigated through considering different sets of building vulnerability curves (provided by HAZUS-MH and various European authors) to characterize the damaging behavior of prevalent building typologies in the city of Bucharest.  相似文献   

Quantifying the error of 2D bulk chondrule analyses using a computer model to simulate chondrules (SIMCHON)     

Dominik C. HEZEL  Ralf KIEßWETTER 《Meteoritics & planetary science》2010,45(4):555-571

Bulk chondrule compositions are important to many questions in cosmochemistry, however, the number of available bulk chondrule data sets is still small. A main reason for this is the difficulties of determining bulk chondrule compositions. A commonly used technique is to obtain 2D bulk chondrule compositions from meteorite sections. This technique has an error that we quantify here for the first time using a mathematical model of a chondrule called SIMCHON. The theoretically calculated errors are compared to errors that we determined from serial sectioning of eight Efremovka chondrules. The errors obtained from both approaches are in excellent agreement, proving that our mathematical model produces reliable errors that can be assigned to 2D bulk chondrule compositions. These errors allow a much better interpretation of 2D bulk chondrule data. We provide a table that contains typical errors for 2D bulk compositions of porphyritic chondrules. The errors are in the range of ±<1–30 relative‐%. This should be acceptable for many problems in cosmochemistry. The effect of a chemical layering inside chondrules and the occurrence of a rim around them, as well as the occurrence of opaque and other accessory phases have been studied. A spreadsheet is provided that enables the calculation of errors for any desired chondrule mineral composition. BO chondrules have a negligible error, but it is impossible to provide reasonable error estimates for BO chondrules with an igneous rim. Radial pyroxene chondrules have negligible errors.  相似文献   

The freshwater balance of polar regions in transient simulations from 1500 to 2100 AD using a comprehensive coupled climate model     

Flavio Lehner  Christoph C. Raible  Dominik Hofer  Thomas F. Stocker 《Climate Dynamics》2012,39(1-2):347-363

The ocean and sea ice in both polar regions are important reservoirs of freshwater within the climate system. While the response of these reservoirs to future climate change has been studied intensively, the sensitivity of the polar freshwater balance to natural forcing variations during preindustrial times has received less attention. Using an ensemble of transient simulations from 1500 to 2100 AD we put present-day and future states of the polar freshwater balance in the context of low frequency variability of the past five centuries. This is done by focusing on different multi-decadal periods of characteristic external forcing. In the Arctic, freshwater is shifted from the ocean to sea ice during the Maunder Minimum while the total amount of freshwater within the Arctic domain remains unchanged. In contrast, the subsequent Dalton Minimum does not leave an imprint on the slow-reacting reservoirs of the ocean and sea ice, but triggers a drop in the import of freshwater through the atmosphere. During the twentieth and twenty-first century the build-up of freshwater in the Arctic Ocean leads to a strengthening of the liquid export. The Arctic freshwater balance is shifted towards being a large source of freshwater to the North Atlantic ocean. The Antarctic freshwater cycle, on the other hand, appears to be insensitive to preindustrial variations in external forcing. In line with the rising temperature during the industrial era the freshwater budget becomes increasingly unbalanced and strengthens the high latitude’s Southern Ocean as a source of liquid freshwater to lower latitude oceans.  相似文献   

Grundschicht und Nullschicht der Atmosphäre     

Prof. Dr. Karl Schneider-Carius  Dr. Heinrich Faust 《Pure and Applied Geophysics》1953,26(1):119-126

Zusammenfassung NachdemSchneider-Carius die von ihm in mehreren Untersuchungen behandelte und von ihm so bezeichnete «Grundschicht» als das Hauptausgleichniveau für die Druckgegensätze zwischen Hoch und Tief in den unteren Luftschichten nachgewiesen hat, entstand naturgemäß die Frage, wie und in welcher Höhensicht der notwendige Massenfluß vom Tief zum Hoch erfolgt. Ohne denselben würden sich die Druckgebilde wegen der ageostrophischen Windkomponente vom Hoch zum Tief in der Grundschicht binnen kürzester Zeit auflösen.H. Faust fand diese Schicht über Mitteleuropa in 10 km Höhe. Sie ist identisch mit dem Sitz des hochtroposphärischen Windmaximums und weist das Maximum des ageostrophischen Massenflusses vom Tief zum Hoch auf. Da in ihr die für das Wettergeschehen so fundamental wichtigen Vertikalbewegungen Null sind, nannteFaust die Schicht «Nullschicht». In der Grundschicht und der Nullschicht sind somit zwei atmosphärische Schichten gefunden, die in polarer Wechselwirkung miteinander für die Dynamik der Wettervorgänge von entscheidender Bedeutung sind.

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Summary Especially whenSchneider-Carius had shown in several papers the ground layer to be the main levelling layer of pressure contrasts, the question arose where the seat of mass transport from low to high pressure is located. ThenFaust found a layer 10 kms above Central Europe, where vertical motion in highreaching cyclones and anticyclones averages zero. Because of the fundamental significance of vertical motion, he called it the «zero layer». This zero layer, which is identical with the wind maximum in the upper troposphere, turned out to be the principal seat of ageostrophic mass transport from low to high pressure. Also, the angle between true and geostrophic wind (the ageostrophic component) has its maximum in the zero layer. As the processes in the zero layer produce and/or increase pressure contrasts, it is the direct counterpart of the ground layer. It is shown that both layers are exercising reciprocal effects upon each other, with action in one layer producing the appropriate reaction in the other layer. As both layers are the principal seat of ageostrophic mass transport between areas of high and low pressure, their mutual action proves to be of basic importance for the dynamics of the whole weather trend.

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Energieakkumulation in Grundschicht und Nullschicht     

Karl Schneider-Carius  Heinrich Faust 《Pure and Applied Geophysics》1956,33(1):245-250

Zusammenfassung Grundschicht und Nullschicht wurden bereits früher als zwei Schichten erkannt, die in bezug auf den Massenhaushalt der hochreichenden Hoch — und Tiefdruckgebiete von polar entgegengesetzter Bedeutung sind: In der Grundschicht erfolgt ein ageostrophischer Massenfluss vom hohen zum tiefen Druck, in der Nulischicht ein solcher vom tiefen zum hohen Druck. Beide Schichten weisen aber auch Gemeinsamkeiten auf. Sie liegen unter den markantesten Inversionen der Troposph?re (Peplopause bzw. Tropopause). Da eine Inversion als Sperrschicht des nach oben gerichteten Flusses der kinetischen Energie wirkt, kommt es unter ihr zu einem Stau kinetischer Energie, der eine ageostrophische Erh?hung der Windgeschwindigkeit gegenüber den vertikal benachbarten Schichten mit sich bringt. Anhaltspunkte für eine derartige Erh?hung der Windgeschwindigkeit unterhalb der Peplopause liegen vor.

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Summary Ground layer and zero layer were recognized in the past already as two layers that are of directly opposite relevance to the mass exchange in high-reaching high and low pressure areas; taking place in the ground layer is an ageostrophic mass transport in the direction high to low pressure, while in the zero layer the opposite motion is accurring, i.e., from low to high pressure. Yet, the two layers have some communities too. They are located below the most significant inversions of the troposphere (Peplopause and/or Tropopause). Since an inversion will act upon the flow upward of kinetic energy as an intercepting layer, a congestion of kinetic energy will be produced below it, involving an ageostrophic increase in the wind speed, as compared with vertically adjoining layers. There are a number of clues for such an increase of wind speed actually occurring below the peplopause.

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Prof. Dr.Karl Schneider-Carius,Bad Kissingen Erhardstr. 3.

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Dr.Heinrich Faust, Deutscher Wetterdienst,Frankfurt a.M., Taunusanlage 18.  相似文献   

The influence of late Quaternary stagnations on clay sedimentation in the eastern Mediterranean sea     

Dr. Janusz Dominik  Dr. Peter Stoffers 《International Journal of Earth Sciences》1979,68(1):302-317

Late Quaternary sapropels of the eastern Mediterranean differ from normal sediments in their clay mineral composition. Clay minerals in the sapropels studied here are only slightly affected, or are not affected at all by diagenetic alteration. This permits the observation of primary differences. During stagnation periods, the contribution of remote or accessory sources was reduced or even absent. Different circulation patterns and, particularly, a general decline in deeper water currents activity might be held responsible for the observed differences in the clay mineral composition of sapropels and normal sediments.

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Zusammenfassung Die quartären Sapropele des östlichen Mittelmeeres unterscheiden sich von den normal marinen Sedimenten in ihrer Tonmineralzusammensetzung. Die hier untersuchten Tone der Sapropele zeigen nur geringe oder gar keine diagenetischen Veränderungen. Diese Tatsache erlaubt, Rückschlüsse auf primäre Unterschiede zu ziehen. Während der Stagnationsperioden war die Zufuhr von Tonen aus entfernten oder weniger wichtigen Liefergebieten stark vermindert. Unterschiedliche Zirkulation, besonders eine geringere Aktivität der Tiefenströmungen, scheinen die Ursache für die beobachteten Unterschiede in der Tonmineralzusammensetzung zwischen Sapropel- und normal-marinen Sedimenten

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Résumé Les sapropels quaternaires de la Méditerranée orientale se distinguent des vases communes par la composition des minéraux argileux. Les argiles des sapropels examinés sont peu affectés par l'altération diagénétique, ce qui permet l'observation de différences primaires.On a conclu, que pendant les périodes de stagnation, la contribution des argiles provenant des sources éloignées ou secondaires, a été réduite ou même interrompue. Différentes conditions de circulation et, avant tout, la réduction d'activité des courants profonds, sont probablement responsables des différences observées dans la composition des minéraux argilezx des sapropels et des vases communes.

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The geochemistry of major and selected trace elements in a forested peat bog, Kalimantan, SE Asia, and its implications for past atmospheric dust deposition     

Dominik Weiss  William ShotykJack Rieley  Susan PageMarlies Gloor  Steve ReeseAntonio Martinez-Cortizas 《Geochimica et cosmochimica acta》2002,66(13):2307-2323

Biogeochemical processes in a forested tropical peat deposit and its record of past atmospheric dust deposition were assessed using the vertical distribution of lithophilic and plant essential elements in a dated core profile from Borneo, SE Asia. Peat formation started ∼22,120 ¹⁴C yr before present (BP), and Ca/Mg mass ratios of the solid peat and very low ash contents indicate a strongly ombrotrophic character throughout the deposit, implying that most of the inorganic fraction has been supplied exclusively by atmospheric inputs. Concentration profiles of Mn, Sr, and Ca suggest a very minor influence of chemical diagenesis in the underlying sediments. Silicon, Ca, Mg, P, S, and K show a strong and extended zone of enrichment in the top 200 cm of the profile, indicating that biological accumulation mechanisms are much more extensive than in temperate peat bogs.In the lower core sections, where the element distribution is dominated solely by past atmospheric deposition, average Al/Ti ratios are similar to the upper continental crust (UCC), whereas Fe is slightly enriched and Si is strongly depleted: this condition favors highly weathered tropical soil dust as the main inorganic mineral source. Significant correlation of Al, Fe, Si, S, Ca, and Ti with the lithophilic elements Y and Zr suggests that the distribution of these elements is controlled by sources of atmospheric mineral dust. The Ca/Mg, Ca/K, and Mg/K ratios of the collected rainwater samples are similar to the global average of continental rainwater and suggest a continental character for the site. This is supported by the similarity of the average concentration of Br, Mg, Ca, and S to that in temperate continental and maritime bogs in Switzerland and Scotland.The concentration profiles of Si, Fe, Al, and Ti show distinct peaks within the profile, implying enhanced dust deposition, reduced rates of peat accumulation, or possibly both owing to climatic changes during the Holocene. Enhanced dust deposition between ∼10,830 and 9060 ¹⁴C yr BP is tentatively interpreted as a Younger Dryas-like event with dust fluxes of ∼10.8 mg/m²/yr. The variations in Al/Ti and Fe/Ti profiles suggest that mineral dust sources have been changing constantly during the Holocene, with local sources being dominant between ∼7820 and 9500 ¹⁴C yr BP and long-range transport (derived most likely from China) being important during the late Pleistocene and early Holocene and from ∼7820 ¹⁴C yr BP to the present.  相似文献