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  • 1
    ISSN: 1432-1157
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Mercury, cadmium, arsenic, and antimony were analyzed in cores sampled on the Azores-Iceland Ridge. High values of 780 μg · kg−1 for Hg, 1.7 μg · g−1 for Cd, 87 μg · g−1 for As, and 8.1 μg · g−1 for Sb occur in the rift valley and transform faults. These enrichments, strictly linked to the ridge, could not have an allochtonous origin. A local hydrogenous flux may explain this phenomenon. These metallic enrichments may be connected to a hydrothermal activity extended between 43° N and 47° N.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1157
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Data obtained from mineralogical and geochemical analyses of piston and gravity cores, recovered from an area off Lisbon (Portugal) to the Alboran Sea (Mediterranean), serve as a basis for better understanding the past 18,000 years of hydrological exchanges at Gibraltar. Tracers used in this study are smectite, kaolinite, Ta, Th, La. One of the primary sources of particles both into and out of the Mediterranean is the Guadalquivir River. These particles are transported back into the Atlantic in the Mediterranean outflow water, and deposited along the Iberian slope. No evidence for reversal of this outflow current was found in those cores, since 18,000 years B.P.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  Methods are described for the accurate and precise determination of lead concentrations and the isotopic composition of lead in wine samples using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). This method needs little sample preparation. A comparison with lead isotope ratios measured by Thermal Ionization Mass Spectrometry (TIMS) in three wine samples reveals a good agreement between the two techniques. The lead concentration in three certified wine samples were measured by isotope dilution (ID) and the results are compared with those obtained by external calibration ICP-MS.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The application of inductively coupled plasma-mass spectrometry (ICP-MS) is documented for the study of the strontium isotopic composition (87Sr/86Sr) in geological samples, i.e. in the marine lithic fraction of core sediments. Methods for the determination of the isotopic composition, its accuracy and precision are reported. The results obtained simultaneously on 11 samples by both ICP-MS and thermal ionization mass spectrometry (TIMS) reveal a very good correlation (r2 = 0.955).
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Holocene aeolian silts deposited on the Cape Verde Islands provide information about the origin of African palaeodusts that have fallen on the north-eastern Atlantic ocean over the last 10 000 years. Sedimentological composition indicates that most of these aeolian silts are unquestionably of continental origin. Their Sr and Nd isotopic composition identifies a Saharan origin-suggesting transport by Harmattan winds. We estimate that Saharan dust comprises 75–95% of material in these Holocene silts, the rest coming from the weathering of local basaltic bedrock.
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  • 6
    ISSN: 1573-2932
    Keywords: Arcachon Lagoon ; atmospheric fluxes ; Cd ; coastal zones ; Cu ; Gironde Estuary ; heavy metals ; high frequency variability ; ICP-MS ; Ni ; Pb ; Zn
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract We report here the first data set on wet deposition of heavy metals in the southwestern French coastal zone. In this region, there are two major sensitive coastal ecosystems: the Gironde Estuary and the Arcachon Lagoon. Chemical analyses of heavy metals were carried out by ICP-MS. Annual mean concentrations of the dissolved fraction in precipitation were 0.2, 3.4, 4.3, 8.1 and 30 μg L-1for Cd, Ni, Cu, Pb and Zn, respectively. In terms of annual fluxes, these numbers are of the same order of magnitude as the fluxes measured in southeastern France, but are higher than those measured in western Brittany. When extrapolated to the entire Bay of Biscay, the annual wet dissolved fluxes of Cd, Ni, Cu, Pb and Zn are respectively 7, 110, 140 340 and 1440 t yr-1. According to available data in the literature, the regional Cd, Cu, Pb and Zn atmospheric fluxes for the Bay of Biscay are of the same order of magnitude as riverine inputs (Loire and Gironde). On a daily or weekly time scale, we observed a strong variability of elemental fluxes: up to 20% of the annual dissolved flux may occur in a rain event shorter than 3.5 days. Although elements display generally parallel variations with time, they sometimes follow independent behaviours (e.g. Pb and Cd), suggesting that they may derive from different geographical and/or pollution sources.
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  • 7
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract A new method analysis used in the study of the El Kef Section (north-western Tunisia) led to the paleooceanographic reconstruction of the Mesogean between-late Cretaceous and early Paleogene. Several changes observed are, in fact, worthy of particular mention: paleobathymetrically the area changed from an upper bathyal environment of about 400 m deep to an outer shelf domain of 100-50 m. Furthermore, the Oxygen Minimum Zone (O.M.Z.) became highly intense at (a) the Cretaceous-Tertiary transition (catastrophic event); (b) the P1-P2 boundary (intense thermic stratification); and (c) between P4 and P6 (very active paleoproductivity). In this last episode the continental shelf environment was subjected to intense upwelling responsible for the formation of a »prephosphatic« environment at water/sediment interface. The paleooceanographic history of phosphates in the Gafsa-Metlaoui basin is, in fact, in perfect stratigraphic and paleoenvironmental agreement with the paleobathymetric evolution of the Kef region. Finally, paleooceanographic communication between the Mesogean and the North Atlantic was, at this period, highly free because of lack of hydrologic relations between the North Atlantic and the Norwegian Sea.
    Abstract: Résumé En utilisant une nouvelle méthodologie pour la faune d'ostracode, nous avons étudié la série sédimentaire du Kef au Nord-ouest de la Tunisie, dans le but de proposer une évolution hypothétique de la paléooceanographie de la Mesogée méridionale entre le Cretacé terminal et le début du Paleogène. Pendant cette période l'environnement a changé sur le plan paléobathymetrique, allant du domaine epibathyal 400 m environ en domaine littoral 100-50 m environ. Sur le plan hydrologique la zone à oxygène minimum (Z.O.M.) a augmenté d'intensité: a) à la limite cretacé tertiaire qui semble être un événement catastrophique; b) à la limite P1-P2 (stratification thermique plus importante); c) entre le milieu de P4 jusqu'à P6 (sous l'effet d'une augmentation de la productivité). Pendant ce deriner episode l'environnement de la plateforme continentale était sous l'effet des resurgences océaniques. En conséquence l'interface eau-sédiment possédait les caractéristiques géochimiques d'un milieu »préphosphatique«. L'histoire paléoocéanographique des phosphates de Gafsa-Metlaoui est en accord stratigraphique et »paléoenvironnemental« avec l'histoire paléobathymétrique de la région du Kef. De plus, les paléocirculations de l'Atlantique Nord induisant des fortes productivités au début de l'Eocène-fin du Paléocène sont en accord avec nos résultats obtenus au Kef.
    Notes: Zusammenfassung Das Profil von El Kef in Nord-West Tunesien wurde mit einer neuen Analysen-Methode studiert. Diese Studie ermöglichte uns eine Rekonstruktion der paläoozeanischen Evolution der Mesogäa zwischen der späten Kreide und dem frühen Paleogen. Während dieser Periode haben sich mehrere Änderungen vollzogen: Tiefenmäßig änderte sich das Gebiet von einem oberen bathyalen Bereich von ungefähr 400 m Tiefe zu einem äußeren Schelf von 100-50 m Tiefe. Außerdem wurde die Zone des minimalen Sauerstoffgehalts (M.O.Z.) sehr ausgeprägt a) im Übergang von der Kreide zum Tertiär durch ein katastrophales Ereignis b) an der P1-P2 Grenzlinie (ausgeprägte thermische Schichtung) c) zwischen P4 und P6 (sehr starke Paläeoproduktivität). In dieser späten Periode wurde die Umwelt des Kontinentalschelfs starkem Upwelling ausgesetzt, auf das die Bildung eines präphosphatischen Milieus im Grenzbereich Wasser/Sediment zurückgeht. Die paläoozeanographische Geschichte der Phosphate im Gafsa-Metlaui-Becken steht schließlich in vollkommener Übereinstimmung mit der paleobathymetrischen Entwicklung der Kef-Region im Hinblick auf die Stratigraphie und das Paläoenvironment. Schließlich war der paläoozeanographische Austausch zwischen der Mesegäa und dem Nordatlantik zu dieser Zeit sehr offen, weil noch keine hydrologischen Beziehungen zwischen dem Nordatlantik und der arktischen See bestanden.
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  • 8
    Publication Date: 2016-09-23
    Description: © 2007 Author(s) et al. This is an open-access article distributed under a Creative Commons License. The definitive version was published in Climate of the Past 3 (2007): 569-575, doi:10.5194/cp-3-569-2007
    Description: Since the first suggestion of 1500-year cycles in the advance and retreat of glaciers (Denton and Karlen, 1973), many studies have uncovered evidence of repeated climate oscillations of 2500, 1500, and 1000 years. During last glacial period, natural climate cycles of 1500 years appear to be persistent (Bond and Lotti, 1995) and remarkably regular (Mayewski et al., 1997; Rahmstorf, 2003), yet the origin of this pacing during the Holocene remains a mystery (Rahmstorf, 2003), making it one of the outstanding puzzles of climate variability. Solar variability is often considered likely to be responsible for such cyclicities, but the evidence for solar forcing is difficult to evaluate within available data series due to the shortcomings of conventional time-series analyses. However, the wavelets analysis method is appropriate when considering non-stationary variability. Here we show by the use of wavelets analysis that it is possible to distinguish solar forcing of 1000- and 2500- year oscillations from oceanic forcing of 1500-year cycles. Using this method, the relative contribution of solar-related and ocean-related climate influences can be distinguished throughout the 10 000 yr Holocene intervals since the last ice age. These results reveal that the 1500-year climate cycles are linked with the oceanic circulation and not with variations in solar output as previously argued (Bond et al., 2001). In this light, previously studied marine sediment (Bianchi and McCave, 1999; Chapman and Shackleton, 2000; Giraudeau et al., 2000), ice core (O'Brien et al., 1995; Vonmoos et al., 2006) and dust records (Jackson et al., 2005) can be seen to contain the evidence of combined forcing mechanisms, whose relative influences varied during the course of the Holocene. Circum-Atlantic climate records cannot be explained exclusively by solar forcing, but require changes in ocean circulation, as suggested previously (Broecker et al., 2001; McManus et al., 1999).
    Description: This work is supported by ANR project: “Integration des contraintes Paleoclimatiques pour reduire les Incertitudes sur l’evolution du Climat pendant les periodes Chaudes”- PICC (ANR-05-BLAN- 0312-02).
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 9
    Publication Date: 2019-07-12
    Description: The concentration of Pb and its isotopic composition were measured in samples from the surface of sea-water sediments obtained from the northeastern Atlantic, the Sargasso Sea, and the U.S. continental shelf, with the purpose of investigating changes in Pb sources due to the anthropogenic perturbation that took place in modern times. It was found that the anthropogenic Pb input to marine sediments due to the increase of Pb contamination over the ocean during the last century could be identified in all these samples. However, samples from eastern and western Atlantic had very different Pb isotopic profiles, each reflecting the character of anthropogenic Pb emissions from the European and U.S. industries, respectively.
    Keywords: ENVIRONMENT POLLUTION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 54; 37-47
    Format: text
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  • 10
    Publication Date: 2019-07-12
    Description: Previous studies have shown that Pb can be used as a transient tracer in the atmosphere and the ocean because of strong time-variability of industrial inputs and because Pb isotopic composition can be used to identify contributions from different sources. Pb isotopic measurements on aerosols collected from the North Atlantic Ocean in the trade wind belt are presented. Aerosols sampled at Barbados during the 1969-1985 period have a Pb isotopic composition different from that observed by previous investigators in Bermuda corals and Sargasso Sea waters. Barbados aerosols appear to contain significant amounts of relatively unradiogenic industrial and automotive Pb that is derived from Europe and carried to Barbados by the trade winds. In contrast, Bermuda corals and Sargasso sea waters are influenced mainly by U.S.-derived emissions, which contain more radiogenic Pb originating from Missouri-type ores. This difference generates a strong latitudinal Europe-U.S.A. isotopic gradient, thus allowing study of trans-Atlantic atmospheric transport and ocean mixing processes.
    Keywords: ENVIRONMENT POLLUTION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 16243-16
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