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  • 1
    Electronic Resource
    Electronic Resource
    The potential formation of acid mine drainage in pyrite-bearing hard-coal tailings under water-saturated conditions: an experimental approach (1997)
    Springer
    Environmental geology 31 (1997), S. 59-65 
    Details
    ISSN: 1432-0495
    Keywords: Key words Pyrite oxidation ; Acid mine drainage ; Tailings ; landfill ; Sealing ; Modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Annually, an amount of approximately 13 million cubic meters of hard-coal tailings must be disposed of in the German Ruhr Valley. Besides the waste of land in a densily populated region, the disposal of the pyrite-bearing material under atmospheric conditions may lead to the formation of acid mine drainage (AMD). Therefore, alternative disposal opportunities are of increasing importance, one of which being the use of tailings under water-saturated conditions, such as in backfilling of abandoned gravel pits or in the construction of waterways. In this case, the oxidation of pyrite, and hence the formation of AMD, is controlled by the amount of oxygen dissolved in the pore water of tailings deposited under water. In case the advective percolation of water is suppressed by sufficient compaction of the tailings, oxygen transport can be reduced to diffusive processes, which are limited by the diffusive flux of dissolved oxygen in equilibrium with the atmospheric pO2. Calculations of the duration of pyrite oxidation based on laboratory experiments have shown that the reduction of oxygen is mainly controlled by the content of organic substance rather than the pyrite content, a fact that is supported by results from oxidation experiments with nitrate. A "worst case" study has lead to the result that the complete oxidation of a 1.5-m layer of hard-coal tailings deposited under water-saturated conditions would take as much as several hundred thousand years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002540050164
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Instationäre Wärmeübertragung mit Erstarrung am Beispiel des Fließvermögens reiner Metalle (1980)
    Springer
    Heat and mass transfer 14 (1980), S. 231-244 
    Details
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Der Einströmvorgang metallischer Schmelzen in horizontale Zylinder wurde bis zu ihrer Erstarrung untersucht. Ein mathematisches Modell beschreibt das Temperaturfeld und die mittleren Geschwindigkeiten in dem Teil des Zylinders, der zu jedem Zeitpunkt gerade gefüllt ist. Damit kann das Fließvermögen als maximale Fließlänge allein aufgrund bekannter Größen berechnet werden. Ein empirischer Wärmeübergangskoeffizient wird nämlich dadurch umgangen, daß ein konzentrischer Luftspalt postuliert wird, der sich durch die Schrumpfung des erstarrten Metallringes bildet. — Gießversuche wurden mit reinen Metallen wie Sn, Pb, Zn und Al bei unterschiedlichen Gießtemperaturen und Druckhöhen durchgeführt. Die Fließfunktion wurde dabei mit kleinen Lichtschranken im zylindrischen Metallkanal (Ø 5 mm) gemessen. Die Abhängigkeit wird von einer allgemeinen Gleichung vorausgesagt, die aus den numerischen Ergebnissen abgeleitet wurde, und auch von ähnlichen Messungen anderer Autoren bestätigt.
    Notes: Abstract The entrance flow of molten metals into horizontal cylinders until their solidification has been studied. A mathematical model describes temperature field and mean velocities in that part of the cylinder just filled at each time. Thus fluidity as maximum flow length can be calculated as a function of known properties only. An empirical heat transfer coefficient is avoided by postulating a concentric air-gap which is formed by thermal contraction of the solidified annulus. — Casting experiments with pure metals such as Sn, Pb, Zn, and Al have been conducted for different temperatures and metal-heads. The flow function was measured with small photo-cells in a cylindrical metal form (ø 5 mm). The dependence of fluidity from material properties and casting parameters is predicted by a general formula, derived from the numerical results, and is verified also by similar experiments by other authors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01618355
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    Paper (German National Licenses)
    Fulltext
  • 3
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    Report and preliminary results of R/V SONNE Cruise SO251 - Extreme events Archived in the GEologial Record of JAPAN's subduction margins (EAGER-JAPAN) (2017)
    In:  Berichte aus dem MARUM und dem Fachbereich Geowissenschaften der Universität Bremen, 318 . UNSPECIFIED, Bremen, 217 pp.
    Details
    Publication Date: 2019-09-23
    Description: Leg A SO251-1, Yokohama - Yokohama, 04.10.2016 - 15.10.2016, Leg B SO251-2, Yokohama - Yokohama, 18.10.2016 - 02.11.2016
    Type: Report , NonPeerReviewed
    Format: text
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    OceanRep: Report - Cruise Report
  • 4
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    Mid- to late Holocene changes in tropical Atlantic temperature seasonality and interannual to multidecadal variability documented in southern Caribbean corals (2012)
    Elsevier
    In:  Earth and Planetary Science Letters, 331-332 . pp. 187-200.
    Details
    Publication Date: 2019-04-09
    Description: Proxy reconstructions of tropical Atlantic sea surface temperature (SST) that extend beyond the period of instrumental observations have primarily focused on centennial to millennial variability rather than on seasonal to multidecadal variability. Here we present monthly-resolved records of Sr/Ca (a proxy of SST) from fossil annually-banded Diploria strigosa corals from Bonaire (southern Caribbean Sea). The individual corals provide time-windows of up to 68 years length, and the total number of 295 years of record allows for assessing the natural range of seasonal to multidecadal SST variability in the western tropical Atlantic during snapshots of the mid- to late Holocene. Comparable to modern climate, the coral Sr/Ca records reveal that mid- to late Holocene SST was characterised by clear seasonal cycles, persistent quasi-biennial and prominent interannual as well as inter- to multidecadal-scale variability. However, the magnitude of SST variations on these timescales has varied over the last 6.2 ka. The coral records show increased seasonality during the mid-Holocene consistent with climatemodel simulations indicating that southern Caribbean SST seasonality is induced by insolation changes on orbital timescales,whereas internal dynamics of the climate system play an important role on shorter timescales. Interannual SST variability is linked to ocean– atmosphere interactions of Atlantic and Pacific origin. Pronounced interannual variability in the western tropical Atlantic is indicated by a 2.35 ka coral, possibly related to a strengthening of the variability of the El Niño/Southern Oscillation throughout the Holocene. Prominent inter- to multidecadal SST variability is evident in the coral records and slightly more pronounced in the mid-Holocene. We finally argue that our coral data provide a target for studying Holocene climate variability on seasonal and interannual to multidecadal timescales, when using further numerical models and high-resolution proxy data.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.epsl.2012.03.019
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Formation pathways of light hydrocarbons in deep sediments of the Danube deep-sea fan, Western Black Sea (2020)
    Elsevier
    Details
    Publication Date: 2023-02-08
    Description: Highlights • MeBo drilling in Danube fan down to 147 m recovered limnic to marine deposits. • Molecular and stable isotope characterization of light hydrocarbons, CO2, and H2O. • H and O isotopic compositions of pore water reflect paleoclimate variations. • Isotope relations prove microbial carbonate reduction as major methanogenic pathway. • Control of δ2H–CH4 by δ2H–H2O may lead to misinterpretation of methanogenic paths. Abstract We report on the geochemistry of light hydrocarbons and pore water in sediments down to 147 m below seafloor (mbsf), at two sites within the gas hydrate stability field of the Danube deep-sea fan, Black Sea. Sediments were drilled with MARUM-MeBo200 and comprise the transition from limnic to the recent marine stage. Stable C/N ratios (mean 5.1 and 5.6) and δ13C-Corg values (mean −25.8‰ V-PDB) suggest relatively uniform bulk organic matter compositions. In contrast, pore water δ2H and δ18O values varied considerably from approx. −120‰ to −30‰ V-SMOW and from −15‰ to −3‰ V-SMOW, respectively. These data pairs plot close to the ‘Global Meteoric Water Line’ and indicate paleo temperature variations. Depletions of pore water in 2H and 18O below 40 mbsf indicate low temperatures and likely reflect conditions during (the) last glacial period(s). Methane was much more abundant than the only other hydrocarbons found in notable concentrations, ethane and propane ((C1/(C2+C3) ≥20,000). Relatively constant δ13C–CH4 (~−70‰ V-PDB) and δ13C–C2H6 (~−52‰ V-PDB) values with depth indicate that methane and ethane are predominantly of microbial origin and that their formation was not limited by carbon availability. In contrast, δ2H–CH4 values varied in a large range (approx. −310 to −240‰ V-SMOW) with depth and positively correlated with trends observed for δ2H–H2O. Isotope separations (Δδ13C(CH4–CO2), Δδ2H(CH4–H2O)) substantiate that microbial carbonate reduction (CR) is the prevalent methanogenic pathway throughout the sediments irrespective of their geochemical history. Remarkably, in δ13C–CH4 – δ2H–CH4 diagrams widely used, samples characterized by δ2H–CH4 values more negative than approx. −250‰ plot out of the field assigned for pure CR. We conclude that assignments of microbial methanogenic pathways based on classical interpretations of δ13C–CH4 – δ2H–CH4 pairs can lead to misinterpretations, as severe 2H-depletions of methane formed through microbial CR can result from 2H-depletions of the pore water generated during low-temperature climatic periods.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    High Carbon Mineralization Rates in Subseafloor Hadal Sediments — Result of Frequent Mass Wasting (2022)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2024-02-07
    Description: In the past 20 years, the exploration of deep ocean trenches has led to spectacular new insights. Even in the deepest canyons, an unusual variety of life and unexpectedly high benthic oxygen consumption rates have been detected while microbial processes below the surface of the hadal seafloor remains largely unknown. The information that exist comes from geophysical measurements, especially related to seismic research, and specific component analyses to estimate the carbon export. In contrast, no information is available on metabolic activities in deeper buried sediments of hadal environment. Here we present the first pore water profiles from 15 up to 11 m long sediment cores recovered during three expeditions to two hadal zones, the Japan Trench and the Atacama Trench. Despite low levels of organic debris, our data reveal that rates of microbial carbon turnover along the trench axes can be similar to those encountered in much shallower and more productive oceanic regions. The extreme sedimentation dynamics, characterized by frequent mass wasting of slope sediments into the trenches, result in effective burial of reactive, microbially available, organic material. Our results document the fueling of the deep hadal biosphere with bioavailable material and thus provide important understanding on the function of deep-sea trenches and the hadal carbon cycle. Key Points Hadal subseafloor pore water profiles from the Japan Trench and Atacama Trench document unexpectedly high microbial turnover rates Frequent alternations between hemipelagic sedimentation and mass wasting lead to high burial efficiency of reactive organic carbon Microbial activities in deep-sea trenches may be similar to those at the edge of high-production areas
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Laboratory experiments for the investigation of barite supersaturation of thermal brines (1997)
    In:  Grundwasser
    Details
    Publication Date: 2020-02-12
    Description: Wie geochemisch-thermodynamische Modellierungen gezeigt haben, können während des Betriebs einer geothermischen Heizanlage durch Druck- und Temperaturveränderungen Baryt, Anhydrit/Gips oder Cölestin ausfallen. Das Fällungsverhalten der Erdalkalisulfate wurde unter In-situ-Bedingungen (Druck, Temperatur, Salinität 216 g/l) in einem Durchströmungsversuch bestimmt. Es wird eine Durchströmungsanlage vorgestellt, die Drucke bis zu 250 bar und hohe Temperaturen bei der Durchströmung eines Sandsteinkerns zuläßt. Ergänzende Fällungsexperimente bestätigen eine zu erwartende Reaktion zweiter Ordnung bei der Kristallisation von Baryt mit einer mittleren Geschwindigkeitskonstanten von 2,5 • 10-4 l mg-1 h-1. Die real lösliche Menge Baryt (2,5 mg/l Ba und 450 mg/l SO4) ist höher als das thermodynamische Gleichgewicht vorhersagt. Cölestin und Anhydrit oder Gipsausfällungen konnten nicht nachgewiesen werden. Bei der Durchströmung des Sandsteinkerns unter In-situ- Bedingungen findet keine Ausfällung von Baryt, Anhydrit/ Gips oder Cölestin statt. Obwohl Kristallisationskeime im Sandstein vorhanden sind, erfolgt keine Fällung aus den metastabilen Lösungen.
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/article
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    GFZ OAI
  • 8
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    Rhizon Sampling of Pore Waters on Scientific Drilling Expeditions: An Example from the IODP Expedition 302, Arctic Coring Expedition (ACEX) (2007)
    In:  Scientific Drilling
    Details
    Publication Date: 2020-02-12
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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    GFZ OAI
  • 9
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    Controls of Caribbean surface hydrology during the mid- to late Holocene: insights from monthly resolved coral records (2013)
    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3Climate of the Past, COPERNICUS GESELLSCHAFT MBH, 9, pp. 841-858, ISSN: 1814-9324
    Details
    Publication Date: 2019-07-17
    Description: Several proxy-based and modeling studies have investigated long-term changes in Caribbean climate during the Holocene, however, very little is known on its variability on short timescales. Here we reconstruct seasonality and interannual to multidecadal variability of sea surface hydrology of the southern Caribbean Sea by applying paired coral Sr/Ca and δ18O measurements on fossil annually banded Diploria strigosa corals from Bonaire. This allows for better understanding of seasonal to multidecadal variability of the Caribbean hydrological cycle during the mid- to late Holocene. The monthly resolved coral Δδ18O records are used as a proxy for the oxygen isotopic composition of seawater (δ18Osw) of the southern Caribbean Sea. Consistent with modern day conditions, annual δ18Osw cycles reconstructed from three modern corals reveal that freshwater budget at the study site is influenced by both net precipitation and advection of tropical freshwater brought by wind-driven surface currents. In contrast, the annual δ18Osw cycle reconstructed from a mid-Holocene coral indicates a sharp peak towards more negative values in summer, suggesting intense summer precipitation at 6 ka BP (before present). In line with this, our model simulations indicate that increased seasonality of the hydrological cycle at 6 ka BP results from enhanced precipitation in summertime. On interannual to multidecadal timescales, the systematic positive correlation observed between reconstructed sea surface temperature and salinity suggests that freshwater discharged from the Orinoco and Amazon rivers and transported into the Caribbean by wind-driven surface currents is a critical component influencing sea surface hydrology on these timescales.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 10
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    Rhizon in situ sampler (RISS) for pore water sampling from aquatic sediments. (2005)
    In:  EPIC3In-situ Methods and Investigations in Environmental Science, 230th Meeting of the American Chemical Society, Division of Geochemistry, 28 Aug. - 1 Sept., Washington, DC, USA.
    Details
    Publication Date: 2019-07-17
    Description: Rhizon soil moisture samplers were successfully used for multi-level pore water sampling from in-situ sediments and sediment cores. By this method, high resolution pore water profiles may be sampled with minimum disturbance of both, the sediment structure and possible flow fields. To investigate biogeochemical cycles, especially at the sediment/water interface, we present a newly developed Rhizon In Situ Sampler (RISS) as a non-destructive tool for in-situ pore water sampling. Field experiments, tracer studies and numerical modeling were combined to assess the suitability of Rhizons for pore water sampling. A combination of a benthic chamber with the RISS allows studies of benthic fluxes and pore water profiles at the exact same location with negligible effect on the incubated sediment/water interface. This allows improved modeling of transport and reaction processes. Long term deployments of the RISS and repetitive pore water sampling will support future studies of the seasonal variation of benthic processes.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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