Iron oxide reduction in methane-rich deep Baltic Sea sediments

Egger, Matthias; Hagens, Mathilde; Sapart, Célia-Julia; Dijkstra, N. D.; Helmond, Niels A. G. M. van; Mogollón, José M; Risgaard-Petersen, Nils; Veen, Carina van der; Kasten, Sabine; Riedinger, Natascha; Böttcher, Michael E.; Röckmann, Thomas; Jørgensen, Bo Barker; Slomp, Caroline P.

doi:10.1016/j.gca.2017.03.019

Cited by 102 publications

(101 citation statements)

References 121 publications

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“…The data files are available from the PANGAEA database (https://doi.org/10.1594/PANGAEA.880135; Dijkstra et al, 2017b) or are already published in Egger et al (2017) or Andrén et al (2015).…”

Section: Discussionmentioning

confidence: 99%

“…The high Fe 2+ concentrations in the Ancylus Lake sediments are assumed to be the result of reductive dissolution of Fe oxides in the lake sediments (Fig. 5) via organoclastic Fe reduction, Fe-mediated anaerobic oxidation of CH 4 or a combination of both (Egger et al, 2017). Although porewater PO 4 already began to accumulate in the surface sediments before the lake-marine transition, following the increase in organic matter inputs at 10 500 years BP, the rate of iron(II)-phosphate formation resulting from this is insignificant compared to the authigenesis taking place directly after the lake-marine transition, explaining the fast increase in iron(II)-phosphate concentration at the interface with the lake sediments (Fig.…”

Section: Post-depositional Formation and Stability Of Vivianite-type mentioning

confidence: 99%

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Post-depositional formation of vivianite-type minerals alters sediment phosphorus records

et al. 2018

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Abstract. Phosphorus (P) concentrations in sediments are frequently used to reconstruct past environmental conditions in freshwater and marine systems, with high values thought to be indicative of a high biological productivity. Recent studies suggest that the post-depositional formation of vivianite, an iron(II)-phosphate mineral, might significantly alter trends in P with sediment depth. To assess its importance, we investigate a sediment record from the Bornholm Basin that was retrieved during the Integrated Ocean Drilling Program (IODP) Baltic Sea Paleoenvironment Expedition 347 in 2013, consisting of lake sediments overlain by brackish-marine deposits. Combining bulk sediment geochemistry with microanalysis using scanning electron microscope energy dispersive spectroscopy (SEM-EDS) and synchrotron-based X-ray absorption spectroscopy (XAS), we demonstrate that vivianite-type minerals rich in manganese and magnesium are present in the lake deposits just below the transition to the brackish-marine sediments (at 11.5 to 12 m sediment depth). In this depth interval, phosphate that diffuses down from the organic-rich, brackish-marine sediments meets porewaters rich in dissolved iron in the lake sediments, resulting in the precipitation of iron(II) phosphate. Results from a reactive transport model suggest that the peak in iron(II) phosphate originally occurred at the lake-marine transition (9 to 10 m) and moved downwards due to changes in the depth of a sulfidization front. However, its current position relative to the lake-marine transition is stable as the vivianite-type minerals and active sulfidization fronts have been spatially separated over time. Experiments in which vivianite was subjected to sulfidic conditions demonstrate that incorporation of manganese or magnesium in vivianite does not affect its susceptibility to sulfide-induced dissolution. Our work highlights that post-depositional formation of iron(II) phosphates such as vivianite has the potential to strongly alter sedimentary P records particularly in systems that are subject to environmental perturbation, such as a change in primary productivity, which can be associated with a lake-marine transition.

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Section: Discussionmentioning

confidence: 99%

Section: Post-depositional Formation and Stability Of Vivianite-type mentioning

confidence: 99%

Post-depositional formation of vivianite-type minerals alters sediment phosphorus records

et al. 2018

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“…With a 1 = 4.2355605, a 2 = 0.1642818, a 3 = ‐0.3525408, and averaged temperature 8 °C, we get D 0 = 0.0413 m 2 /year. The parameters of porosity, temperature, and sedimentation rate used in the model are slightly different from those used by Egger et al ().…”

Section: Methodsmentioning

confidence: 99%

Holocene Hydrographic Variations From the Baltic‐North Sea Transitional Area (IODP Site M0059)

Krupinski

Groeneveld

et al. 2020

Paleoceanog and Paleoclimatol

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Deoxygenation affects many continental shelf seas across the world today and results in increasing areas of hypoxia (dissolved oxygen concentration ([O2]) <1.4 ml/L). The Baltic Sea is increasingly affected by deoxygenation. Deoxygenation correlates with other environmental variables such as changing water temperature and salinity and is directly linked to ongoing global climate change. To place the ongoing environmental changes into a larger context and to further understand the complex Baltic Sea history and its impact on North Atlantic climate, we investigated a high accumulation‐rate brackish‐marine sediment core from the Little Belt (Site M0059), Danish Straits, NW Europe, retrieved during the Integrated Ocean Drilling Program (IODP) Expedition 347. We combined benthic foraminiferal geochemistry, faunal assemblages, and pore water stable isotopes to reconstruct seawater conditions (e.g., oxygenation, temperature, and salinity) over the past 7.7 thousand years (ka). Bottom water salinity in the Little Belt reconstructed from modeled pore water oxygen isotope data increased between 7.7 and 7.5 ka BP as a consequence of the transition from freshwater to brackish‐marine conditions. Salinity decreased gradually (from 30 to 24) from 4.1 to ~2.5 ka BP. By using the trace elemental composition (Mg/Ca, Mn/Ca, and Ba/Ca) and stable carbon and oxygen isotopes of foraminiferal species Elphidium selseyensis and E. clavatum, we identified that generally warming and hypoxia occurred between about 7.5 and 3.3 ka BP, approximately coinciding in time with the Holocene Thermal Maximum (HTM). These changes of bottom water conditions were coupled to the North Atlantic Oscillation (NAO) and relative sea level change.

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“…Indeed, the dissolved Fe concentrations in porewater below the SMTZ at Sites U1343 and U1344 imply that dissimilatory iron reduction occurs below the SMTZ. Recent studies have suggested the novel process of anaerobic oxidation of methane coupled to reduction of Fe (oxyhydr) oxides also releases dissolved Fe (Fe 2+ ) below SMTZs (e.g., Riedinger et al, 2014;Egger et al, 2017). In this case, Fe(III) in clay minerals would not be the major electron acceptor.…”

Section: Fe(iii) Reduction In Clay Minerals Below the Sulfate-methanementioning

confidence: 99%

Low-Temperature Clay Mineral Dehydration Contributes to Porewater Dilution in Bering Sea Slope Subseafloor

et al. 2018

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Widespread diagenesis of clay minerals occurs in deeply buried marine sediments under high-temperature and high-pressure conditions. For example, the smectite-to-illite (S-I) transformation has been often observed in sediments at in situ temperatures above ∼60 • C. However, it remains largely unknown whether such diagenetic processes naturally occur in relatively shallow and low-temperature sediments and, if so, what the consequences are of any related chemical reactions to the geochemical characteristics in the deep biosphere. We evaluated the possibility of naturally occurring S-I transformation at temperatures below 40 • C in continental slope sediments of the Bering Sea by examining porewater chemistry, clay mineralogy, and chemical composition of clay minerals measured to ∼800 m beneath the seafloor (mbsf) in core samples acquired during Integrated Ocean Drilling Program Expedition 323. In porewater from these cores, chloride concentrations decreased with increasing depth from 560 mM near the seafloor to 500 mM at ∼800 mbsf; δ 18 O increased from 0 to 1.5‰; and δD decreased from −1 to −9‰. These trends are consistent with the addition of water derived from S-I transformation. The discrete low Cl − spikes observed between ∼200 and ∼450 mbsf could be attributed to the dissociation of methane hydrate. X-ray diffraction analysis of the clay-size fraction (<2 µm) showed an increase of illite content in the I/S mixed layer with increasing depth to 150 mbsf. This increase may imply the occurrence of S-I transformation. The decrease of Fe 3+ /Fe 2+ in the clay-size fraction with increasing depth strongly suggests microbial reduction of Fe(III) in clay minerals with burial, which also has the potential to promote the S-I transformation. Our results imply the significant ecological roles on the diagenesis of siliciclastic clay minerals underlying the high-productivity surface seawater at continental margins.

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Iron oxide reduction in methane-rich deep Baltic Sea sediments

Cited by 102 publications

References 121 publications

Post-depositional formation of vivianite-type minerals alters sediment phosphorus records

Post-depositional formation of vivianite-type minerals alters sediment phosphorus records

Holocene Hydrographic Variations From the Baltic‐North Sea Transitional Area (IODP Site M0059)

Low-Temperature Clay Mineral Dehydration Contributes to Porewater Dilution in Bering Sea Slope Subseafloor

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