Reactive iron in Black Sea Sediments: implications for iron cycling |
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| Institution: | 1. Yale University, Department of Earth and Planetary Sciences, New Haven, CT, USA;2. University of Calgary, Department of Geoscience, Calgary, AB, Canada;3. University of Minnesota, Department of Earth and Environmental Sciences, Minneapolis, MN, USA;1. Institute of Oceanography, National Taiwan University, No. 1, Section 4, Roosevelt Rd., Taipei 106, Taiwan;2. Department of Geosciences, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 106, Taiwan;3. Chien-Hsin University of Science and Technology, Taiwan;1. School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA;2. Coastal Studies Institute and Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803, USA;3. Woods Hole Oceanographic Institution, Woods Hole, MA 02543-1050, USA;4. Department of Geosciences, Virginia Polytechnic and State University, Blacksburg, VA 24061, USA;5. School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, USA;1. School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332-0340, USA;2. Ocean Technology Research Program, Mote Marine Laboratory, Sarasota, FL 34236, USA;3. IFREMER, Centre de Bretagne, REM/GM Laboratoire Cycles Géochimiques et Ressources, F-29280 Plouzané, France;4. Institute of Oceanography, Hellenic Center for Marine Research, Anavyssos Attiki, Greece;5. Laboratoire des Sciences de l′Environnement Marin, CNRS-UBO, Institut Universitaire Européen de la Mer, F-29280 Plouzané, France;6. IFREMER, Centre de Bretagne, REM/EEP Laboratoire Environnement Profond, F-29280 Plouzané, France;7. Laboratoire des Sciences du Climat et de l′Environnement, CEA-CNRS-UVSQ, F-91198 Gif sur Yvette, France |
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| Abstract: | The distribution of reactive iron in sediments of the northwestern shelf, the shelf edge and the abyssal part of the Black Sea has been studied. In the euxinic Black Sea, iron sulfides (pyrite and iron monosulfide) are formed in the upper part of the anoxic water column and sink to the deep-sea floor where they are buried in the sediment. This flux of iron sulfides from the water column is reflected in enhanced concentrations of highly reactive iron and a high degree of pyritization (0.57–0.80) for the deep-water sediments of the Black Sea. The iron enrichment of deep-water sediments is balanced by a loss of highly reactive iron from the oxic continental shelf. Calculations from a numerical diagenetic model and reported in situ flux measurements indicate that the dissolved iron flux out of the shelf sediments is more than sufficient to balance the enrichment in reactive iron in deep-sea sediments, and that the majority of the dissolved iron efflux is redeposited on the continental shelf. This iron mobilization mechanism likely operates in most shelf areas, but its net effect becomes only apparent when reactive iron is trapped in sulfidic water bodies as iron sulfides or when iron is incompletely oxidized in low oxygen zones of the ocean and transported over long distances. |
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