Description: Das Projekt "Sources and reaction pathways of soluble Fe from the Western Antarctic Peninsula to the Southern Ocean" wird vom Umweltbundesamt gefördert und von Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung durchgeführt. During two campaigns on King George Island (Antarctica) in 2012 and 2013, numerous sediment and pore water samples were collected in Potter Cove and Maxwell Bay. Especially Potter Cove is strongly affected by glacier retreat, which is assumed to affect the biogeochemical processes in the area. Based on pore water profiles the degradation of sedimentary organic matter in the sediments in proximity to the marine-terminating Fourcade Glacier was found to be dominated by dissimilatory iron reduction (DIR). In contrast, sulfate reduction was apparent at shallow sediment depths in those parts of Potter Cove, where surficial meltwater streams discharge. Sediments in proximity to the glacier fronts contain significantly higher amounts of easily reducible (amorphous) Fe oxyhydroxides than stations in the central part of the bay or in discharge areas of surficial meltwater streams. Stable iron isotopes are considered a proxy for Fe sources, but respective data are scarce and Fe-cycling in complex natural environments is not understood well enough yet to constrain respective delta56Fe 'endmembers' for different types of sediments and environmental conditions. In order to enhance the usability of iron isotopes as proxies for iron sources and reaction pathways, we developed a new method that allows to measure delta56Fe on sequentially extracted sedimentary Fe phases and applied the new protocol to sediment from King George Island. We suggest that easily reducible Fe in proximity to the glacier front is mostly delivered from subglacial sources, where iron liberation from comminuted material beneath the glacier is coupled to biogeochemical weathering processes (pyrite oxidation or DIR). Our strongest argument for a subglacial source of the highly reactive iron pool in sediments close to the glacier front is its overall negative delta56Fe signature that remains constant over the whole ferruginous zone. This pattern implies that the supply with easily reducible Fe exceeds the fraction that afterwards undergoes early diagenetic DIR by far. The light delta56Fe values of easily reducible Fe oxides imply pre-depositional microbial cycling as it occurs in potentially anoxic subglacial environments. Interestingly, the strongest 56Fe-depletion in pore water and of the most reactive Fe oxides was observed in sediments influenced by oxic meltwater discharge. In terms of the potential of delta56Fe as a proxy for benthic Fe fluxes, the study demonstrates limitations due to a large variability of pore water delta56Fe deriving from DIR in the marine sediments at small spatial distances. The controlling factors are multi-fold and include the availability of reducible Fe oxides and organic matter, the isotopic composition of the primary ferric substrate, sedimentation rates, and physical reworking (bioturbation, ice scraping). Whereas delta56Fe may prove a valuable parameter to further investigate biochemical weathering of glacier beds, a quantification of benthic Fe fluxes bas
Types:
SupportProgram
Origin: /Bund/UBA/UFORDAT
Tags: Tierhaltungsanlage ? Benthal ? Eisenoxid ? Substrat ? Silikat ? Eisen ? Antarktische Halbinsel ? Fischer-Tropsch-Verfahren ? Geochemie ? Kontinentalschelf ? Meeressediment ? Oxid ? Skigebiet ? Beleuchtung ? Brunnen ? Anaerobe Bedingungen ? Island ? Abfluss ? Flüssigkeitschromatografie ? Gletscher ? Licht ? Plankton ? Schmelzwasser ? Organisches Material ? Teich ? Bucht ? Eis ? Insel ? Halbinsel ? Feststoff ? Globale Erwärmung ? Antarktis ? Arktis ? Gletscherschwund ? Pyrit ? Meeresforschung ? Isotop ? Oxidation ? Studie ? Versorgung ? Wasserprobe ? Sediment ? Meeresgewässer ? Wasser ? Verwitterung ? Wirkung ? Auflösen ? Gewässergrund ? Wetter ? Sedimentation ? Kenngröße ? Umwelt ? Wiederaufarbeitung ? Anreicherung ? Infrastruktur ? Gebiet ? Diffusion ? Potenzial ? Maßnahme ? Produktivität ? Südlicher Ozean ? Fahrradfahren ? Haltestelle ? Fluss [Bewegung] ? stillgelegt ? Teil ? angewandt ? Überreste ? sedimentär ? Mechanismen ? biogeochemisch ? Verringerung ? Methode ? Wiederaufbereitung ? Bram-Verfahren ? stark ? Pfad ? Adsox-Verfahren ? Primärfaktor ? Quellen ? Stall ? Zustandsdaten ? Säule ? Eignungsprüfung ? gemischt ?
Region: Bremen
Bounding box: 8.83333° .. 8.83333° x 53.08333° .. 53.08333°
License: cc-by-nc-nd/4.0
Language: Deutsch
Time ranges: 2010-01-01 - 2015-12-31
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