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Early diagenetic processes generate iron and manganese oxide layers in the sediments of Lake Baikal, Siberia

Publikationsart Peer-reviewed
Publikationsform Originalbeitrag (peer-reviewed)
Publikationsdatum 2014
Autor/in Torres Natascha T., Och Lawrence M., Hauser Peter C., Furrer Gerhard, Brandl Helmut, Vologina Elena, Sturm Michael, Bürgmann Helmut, Müller Beat,
Projekt Quantification of environmental effects on the weathering state of rock surfaces
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Originalbeitrag (peer-reviewed)

Zeitschrift Environmental Science - Processes & Impacts
Volume (Issue) 16
Seite(n) 879 - 889
Titel der Proceedings Environmental Science - Processes & Impacts
DOI 10.1039/c3em00676j

Abstract

Distinct layers of iron(III) and manganese(IV) (Fe/Mn) oxides are found buried within the reducing part of the sediments in Lake Baikal and cause considerable complexity and steep vertical gradients with respect to the redox sequence. For the on-site investigation of the responsible biogeochemical processes, we applied filter tube samplers for the extraction of sediment porewater combined with a portable capillary electrophoresis instrument for the analyses of inorganic cations and anions. On the basis of the new results, the sequence of diagenetic processes leading to the formation, transformation, and dissolution of the Fe/Mn layers was investigated. With two exemplary cores we demonstrate that the dissolution of particulate Fe and Mn is coupled to the anaerobic oxidation of CH4 (AOM) either via the reduction of sulphate (SO4-2) and the subsequent generation of Fe(II) by S(II) oxidation, or directly coupled to Fe reduction. Dissolved Fe(II) diffuses upwards to reduce particulate Mn(IV) thus forming a sharp mineral boundary. An alternative dissolution pathway is indicated by the occurrence of anaerobic nitrification of NH4+ observed at locations with Mn(IV). Furthermore, the reasons and consequences of the non-steadystate sediment pattern and the resulting redox discontinuities are discussed and a suggestion for the burial of active Fe/Mn layers is presented.
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