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  • 2010-2014  (3)
  • 1995-1999  (2)
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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
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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
  • 3
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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
  • 4
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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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    PAPER (OA)
  • 5
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    Mg/Ca ratios of single planktonic foraminifer shells and the potential to reconstruct the thermal seasonality of the water column (2011)
    In:  EPIC3Paleoceanography, 26, PA3218
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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    PAPER (OA)
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