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  • ACS (American Chemical Society)  (1)
  • Kiel : GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel  (1)
  • Nature Research  (1)
  • 2020-2024  (3)
Document type
Keywords
Publisher
Language
Years
Year
  • 1
    Online Resource
    Online Resource
    MiningImpact 2 - Environmental impacts and risks of deep-sea mining : Abschlussbericht : Vorhabenbezeichnung: Mn-Monstr - Monitoringkonzepte für einen Manganknollenabbau in der Tiefsee : Laufzeit des Vorhabens: 1.8.2018-28.2.2022 (2022)
    Kiel : GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
    Details Availability
    Keywords: Forschungsbericht ; Meeresbergbau ; Umweltbelastung
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (39 Seiten, 1,58 MB) , Illustrationen, Diagramme
    URL: https://edocs.tib.eu/files/e01fb23/1867481707.pdf
    URL: https://doi.org/10.2314/KXP:1867481707
    DOI: 10.2314/KXP:1867481707
    Language: German , English
    Note: Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden , Förderkennzeichen BMBF 03F0812A , Verbundnummer 01183428 , Sprache der Kurzfassungen: Deutsch, Englisch
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  • 2
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    Persistence of plastic debris and its colonization by bacterial communities after two decades on the abyssal seafloor (2020)
    Nature Research
    Details
    Publication Date: 2023-02-08
    Description: The fate of plastic debris entering the oceans is largely unconstrained. Currently, intensified research is devoted to the abiotic and microbial degradation of plastic floating near the ocean surface for an extended period of time. In contrast, the impacts of environmental conditions in the deep sea on polymer properties and rigidity are virtually unknown. Here, we present unique results of plastic items identified to have been introduced into deep-sea sediments at a water depth of 4150 m in the eastern equatorial Pacific Ocean more than two decades ago. The results, including optical, spectroscopic, physical and microbial analyses, clearly demonstrate that the bulk polymer materials show no apparent sign of physical or chemical degradation. Solely the polymer surface layers showed reduced hydrophobicity, presumably caused by microbial colonization. The bacterial community present on the plastic items differed significantly (p 〈 0.1%) from those of the adjacent natural environment by a dominant presence of groups requiring steep redox gradients (Mesorhizobium, Sulfurimonas) and a remarkable decrease in diversity. The establishment of chemical gradients across the polymer surfaces presumably caused these conditions. Our findings suggest that plastic is stable over extended times under deep-sea conditions and that prolonged deposition of polymer items at the seafloor may induce local oxygen depletion at the sediment-water interface.
    Type: Article , PeerReviewed
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Production Method under Surveillance: Laboratory Pilot-Scale Simulation of CH 4 –CO 2 Exchange in a Natural Gas Hydrate Reservoir (2021)
    ACS (American Chemical Society)
    Details
    Publication Date: 2024-02-07
    Description: The "guest exchange"of methane (CH4) by carbon dioxide (CO2) in naturally occurring gas hydrates is seen as a possibility to concurrently produce CH4 and sequester CO2. Presently, process evaluation is based on CH4-CO2 exchange yields of small-or medium-scale laboratory experiments, mostly neglecting mass and heat transfer processes. This work investigates process efficiencies in two large-scale experiments (210 L sample volume) using fully water-saturated, natural reservoir conditions and a gas hydrate saturation of 50%. After injecting 50 kg of heated CO2 discontinuously (E1) and continuously (E2) and a subsequent soaking period, the reservoir was depressurized discontinuously. It was monitored using electrical resistivity, temperature and pressure sensors, and fluid flow and gas composition measurements. Phase and component inventories were analyzed based on mass and volume balances. The total CH4 production during CO2 injection was only 5% of the initial CH4 inventory. Prior to CO2 breakthrough, the produced CH4 roughly equaled dissolved CH4 in the produced pore water, which balanced the volume of the injected CO2. After CO2 breakthrough, CH4 ratios in the released CO2 quickly dropped to 2.0-0.5 vol %. The total CO2 retention was the highest just before the CO2 breakthrough and higher in E1 where discontinuous injection improved the distribution of injected CO2 and subsequent mixed hydrate formation. The processes were improved by the succession of CO2 injection by controlled degassing at stability limits below that of the pure CH4 hydrate, particularly in experiment E2. Here, a more heterogeneous distribution of liquid CO2 and larger availability of free water led to smaller initial degassing of liquid CO2. This allowed for quick re-formation of mixed gas hydrates and CH4 ratios of 50% in the produced gases. The experiments demonstrate the importance of fluid migration patterns, heat transport, sample inhomogeneity, and secondary gas hydrate formation in water-saturated sediments.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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