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  • 1
    Digitale Medien
    Digitale Medien
    Reduced meltwater outflow from the Laurentide ice margin during the Younger Dryas (1996)
    [s.l.] : Nature Publishing Group
    Nature 381 (1996), S. 774-777 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] The Laurentide ice retreat during the last deglaciation was accompanied by the discharge of large amounts of melt water into the North Atlantic and adjacent basins5. The Mississippi river constituted a major outlet for this melt water until the eastward axis of the Great Lake-St Lawrence river axis ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/381774a0
    Standort Signatur Einschränkungen Verfügbarkeit
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    Artikel (Nationallizenzen)
    Volltext
  • 2
    Digitale Medien
    Digitale Medien
    Nitrate cycling in streams: using natural abundances of NO3--δ15N to measure in-situ denitrification (1998)
    Springer
    Biogeochemistry 43 (1998), S. 273-292 
    Details
    ISSN: 1573-515X
    Schlagwort(e): denitrification ; nitrate ; nitrogen isotopes ; N cycling ; 15N
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract Contamination of surface- and groundwaters as a result of anthropogenic nitrate loading is of concern in regions subjected to intense agricultural activities. The capacity of watersheds to absorb, process or release nitrate to outflow drainage waters, however, is poorly constrained. An investigation of in-stream denitrification was conducted in a small stream draining a heavily fertilized agricultural watershed by analyzing natural isotopic abundances of nitrate-nitrogen. Using δ15N isotopic signatures, we show that denitrification plays a large role in reducing nitrate levels during stream transport over a relatively short distance. We found in-situ nitrate losses of up to 50% and a corresponding shift in NO3--δ15N values of 10‰ over a 600 m distance downstream consistent with denitrification. Our results suggest that in-stream nitrate losses must be considered when examining nitrate cycling and contamination in watersheds. Not only should attempts to identify nitrate contamination sources using NO3--δ15N signatures be carried out with caution (as nitrate-N isotopic values can be altered during stream transport such that they no longer reflect the original nitrate source), but in-stream measures of nitrate concentrations aimed at monitoring contamination levels may underestimate nitrate inputs to surface waters due to denitrification during transport.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006036706522
    Standort Signatur Einschränkungen Verfügbarkeit
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    Artikel (Nationallizenzen)
    Volltext
  • 3
    facet.materialart.
    Unbekannt
    Nd and Sm content and isotopic composition of the carbonate-free clay fraction of sediment core HU90-013-013 (1999)
    PANGAEA
    In:  Supplement to: Fagel, Nathalie; Innocent, Christophe; Stevenson, Ross K; Hillaire-Marcel, Claude (1999): Deep circulation changes in the Labrador Sea since the Last Glacial Maximum: New constraints from Sm-Nd data on sediments. Paleoceanography, 14(6), 777-788, https://doi.org/10.1029/1999PA900041
    Details
    Publikationsdatum: 2024-05-18
    Beschreibung: Sm-Nd concentrations and Nd isotopes were investigated in the fine fraction of two Labrador Sea cores to reconstruct the deep circulation patterns through changes in sedimentary supply since the last glacial stage. Three sources are involved: the North American Shield, Palaeozoic rocks from northeastern Greenland, and mid-Atlantic volcanism. The variable input of these sources provides constraints on the relative sedimentary supply, in conjunction with inception of deep currents. During the last glacial stage a persistent but sluggish current occurred inside the Labrador Basin. An increasing discharge of volcanic material driven by the North East Atlantic Deep Water is documented since 14.3 kyr, signaling the setup of a modern-like deep circulation pattern throughout the Labrador, Irminger, and Iceland basins. During the last deglacial stage the isotopic record was punctually influenced by erosion processes related mainly to ice-sheet instabilities, especially 11.4, 10.2, and 9.2 kyr ago.
    Schlagwort(e): Age, 14C milieu/reservoir corrected (-400 yr); Age, dated; Age, mineral; Calendar age; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; HU90-13-013; HUD90/13; Hudson; Marine isotopic stage; Neodymium; Neodymium-143/Neodymium-144 ratio; Neodymium-143/Neodymium-144 ratio, error; Northwest Atlantic; PC; Piston corer; Samarium; Samarium-147/Neodymium-144 ratio; ε-Neodymium
    Materialart: Dataset
    Format: text/tab-separated-values, 555 data points
    Standort Signatur Einschränkungen Verfügbarkeit
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    DATA PANGAEA
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