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RESEARCH PRODUCT

Mn, Fe, Zn and As speciation in a fast-growing ferromanganese marine nodule

Alain ManceauMatthew A. MarcusMichael Kersten

subject

Nodule (geology)BirnessiteXASInorganic chemistrychemistry.chemical_elementManganese010501 environmental sciencesengineering.material010502 geochemistry & geophysics01 natural sciencesFerromanganeseMetalFerrihydriteXAS EXAFS marine ferromanganese nodule Baltic sea speciation[SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/GeochemistryGeochemistry and Petrology0105 earth and related environmental sciencesX-ray absorption spectroscopyBaltic seaExtended X-ray absorption fine structureRadiochemistrymarine ferromanganese nodule6. Clean waterEXAFSspeciationchemistryvisual_artEarth Sciencesvisual_art.visual_art_mediumengineeringEnvironmental science

description

The speciation of Mn, Fe, As and Zn in a fast-growing (0.02mm/yr), shallow-marine ferromanganese nodule has been examined by micro X-ray fluorescence, micro X-ray diffraction, and micro X-ray absorption spectroscopy. This nodule exhibits alternating Fe-rich and Mn-rich layers reflecting redox variations in water chemistry. Fe occurs as two-line ferrihydrite. The As is strictly associated with Fe and is mostly pentavalent, with an environment similar to that of As sorbed on or coprecipitated with synthetic ferrihydrite. The Mn is in the form of turbostratic birnessite with ~;10 percent trivalent manganese in the layers and probably ~;8 percent corner-sharing metal octahedra in the interlayers. The Zn is enriched on the rim of the nodule, associated with Mn. The Zn is completely (>90 percent) tetrahedrally coordinated and sorbed in the interlayers of birnessite on vacant layer Mn sites. The Zn and Mn species are similar to ones found in soils, suggesting common structural principles, despite the differing formation conditions in these systems.

https://doi.org/10.1016/j.gca.2004.01.015