Lake Medard (LM), a post-mining lake in Czech Republic with stratified, sulfate- and ferrous iron-rich bottom waters, serves as a natural laboratory to study sediment-water interface (SWI) dynamics where steep aqueous redox gradients are present. This study investigated the interplay of redox conditions, microbial activity, and sedimentary processes, revealing that short-term Eh fluctuations (80-100 mV) in the bottom water significantly mobilize rare earth elements (REE) and influence the partitioning of other redox-sensitive elements such as vanadium (V) and arsenic (As) from reactive iron (Fe)- and manganese (Mn)-oxyhydroxides during early diagenesis.While carbonate phases like siderite primarily retain their REE signatures, they can incorporate REE released during these redox shifts. Spectroscopic analyses confirmed the presence of FeOOH polymorphs (goethite and lepidocrocite) in organo-mineral aggregates in the upper sediments. Sequential extractions showed that under stronger reducing conditions ( Eh ≈ −190 mV), As predominantly associates with carbonates, shifting to Fe(III)-oxyhydroxides at higher Eh (≈ −80 mV). Isotopic analyses (δ¹³C) indicate that the bulk sediment carbonate is detrital, sourced from Miocene strata. Authigenic pyrite in LM sediments exhibits δ34Spy values (-35.1 to -23.0 ‰), reflecting microbial sulfate reduction. However, the accumulation of the byproduct sulfide, and thus pyrite stabilization, is limited by the low availability of labile organic substrates and the reoxidation of sulfide by Fe(III)-oxyhydroxides. These findings highlight the sensitivity of geochemical signals in sediments to subtle redox shifts and improve our interpretation of ancient deposits formed under dynamic water column redox conditions.
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Research Article|
April 24, 2025
Early Publication
Redox Dynamics and Metal Cycling in the Carbonate-Buffered Sediment-Water Interface of the Ferruginous and Sulfatic Lake Medard, Czech Republic Available to Purchase
D.A. Petrash;
D.A. Petrash
1
Czech Geological Survey, 152 00 Prague, Czech Republic
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A. Valero;
A. Valero
2
Biology Centre, Czech Academy of Sciences, 370 05 České Budějovice, Czech Republic
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K. Umbria-Salinas;
K. Umbria-Salinas
2
Biology Centre, Czech Academy of Sciences, 370 05 České Budějovice, Czech Republic
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C. Thomazo;
C. Thomazo
1
Czech University of Life Sciences, 165 00 Prague, Czech Republic
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T.B. Meador;
T.B. Meador
2
Biology Centre, Czech Academy of Sciences, 370 05 České Budějovice, Czech Republic
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F. Laufek;
F. Laufek
1
Czech Geological Survey, 152 00 Prague, Czech Republic
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J.J. Valdés;
J.J. Valdés
2
Biology Centre, Czech Academy of Sciences, 370 05 České Budějovice, Czech Republic
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V. Chrastný;
V. Chrastný
1
Czech University of Life Sciences, 165 00 Prague, Czech Republic
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K.O. Konhauser
K.O. Konhauser
2
University of Alberta, T6G 2E3 Edmonton AB, Canada
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D.A. Petrash
1
Czech Geological Survey, 152 00 Prague, Czech Republic
A. Valero
2
Biology Centre, Czech Academy of Sciences, 370 05 České Budějovice, Czech Republic
K. Umbria-Salinas
2
Biology Centre, Czech Academy of Sciences, 370 05 České Budějovice, Czech Republic
C. Thomazo
1
Czech University of Life Sciences, 165 00 Prague, Czech Republic
T.B. Meador
2
Biology Centre, Czech Academy of Sciences, 370 05 České Budějovice, Czech Republic
F. Laufek
1
Czech Geological Survey, 152 00 Prague, Czech Republic
J.J. Valdés
2
Biology Centre, Czech Academy of Sciences, 370 05 České Budějovice, Czech Republic
V. Chrastný
1
Czech University of Life Sciences, 165 00 Prague, Czech Republic
K.O. Konhauser
2
University of Alberta, T6G 2E3 Edmonton AB, Canada
Publisher: SEPM Society for Sedimentary Geology
Revision Received:
15 Apr 2024
Accepted:
17 Apr 2024
Received:
27 Nov 2024
First Online:
24 Apr 2025
Online ISSN: 1938-3681
Print ISSN: 1527-1404
© SEPM Society for Sedimentary Geology
Journal of Sedimentary Research (2025)
Article history
Revision Received:
15 Apr 2024
Accepted:
17 Apr 2024
Received:
27 Nov 2024
First Online:
24 Apr 2025
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CitationD.A. Petrash, A. Valero, K. Umbria-Salinas, C. Thomazo, T.B. Meador, F. Laufek, J.J. Valdés, V. Chrastný, K.O. Konhauser; Redox Dynamics and Metal Cycling in the Carbonate-Buffered Sediment-Water Interface of the Ferruginous and Sulfatic Lake Medard, Czech Republic . Journal of Sedimentary Research 2025; doi: https://doi.org/10.2110/jsr.2024.155
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