Depth and intensity of the sulfate-methane transition zone control sedimentary molybdenum and uranium sequestration in a eutrophic low-salinity setting

Jokinen, Sami A.; Koho, Karoliina A.; Virtasalo, Joonas J.; Jilbert, Tom

doi:10.1016/j.apgeochem.2020.104767

Cited by 15 publications

(20 citation statements)

References 147 publications

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“…During each campaign, the first core was used for bottomwater and pore-water sampling using Rhizons™ at 2 cm vertical resolution. The samples were collected into 10 mL polyethylene syringes through pre-drilled holes (diameter 4 mm; e.g., Jokinen et al, 2020) immediately after core retrieval. Within a few hours after retrieval, all water samples were transferred into 15 mL polypropylene centrifuge tubes and acidified to 1 M HNO 3 for elemental analyses.…”

Section: Samplingmentioning

confidence: 99%

Drought recorded by Ba∕Ca in coastal benthic foraminifera

et al. 2022

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Abstract. Increasing occurrences of extreme weather events, such as the 2018 drought over northern Europe, are a concerning issue under global climate change. High-resolution archives of natural hydroclimate proxies, such as rapidly accumulating sediments containing biogenic carbonates, offer the potential to investigate the frequency and mechanisms of such events in the past. Droughts alter the barium (Ba) concentration of near-continent seawater through the reduction in Ba input from terrestrial runoff, which in turn may be recorded as changes in the chemical composition (Ba/Ca) of foraminiferal calcium carbonates accumulating in sediments. However, so far the use of Ba/Ca as a discharge indicator has been restricted to planktonic foraminifera, despite the high relative abundance of benthic species in coastal, shallow-water sites. Moreover, benthic foraminiferal Ba/Ca has mainly been used in open-ocean records as a proxy for paleo-productivity. Here we report on a new geochemical data set measured from living (CTG-labeled) benthic foraminiferal species to investigate the capability of benthic Ba/Ca to record changes in river runoff over a gradient of contrasting hydroclimatic conditions. Individual foraminifera (Bulimina marginata, Nonionellina labradorica) were analyzed by laser-ablation ICP-MS over a seasonal and spatial gradient within Gullmar Fjord, Swedish west coast, during 2018–2019. The results are compared to an extensive meteorological and hydrological data set, as well as sediment and pore-water geochemistry. Benthic foraminiferal Ba/Ca correlates significantly to riverine runoff; however, the signals contain both spatial trends with distance to Ba source and species-specific influences such as micro-habitat preferences. We deduce that shallow-infaunal foraminifera are especially suitable as proxy for terrestrial Ba input and discuss the potential influence of water-column and pore-water Ba cycling. While distance to Ba source, water depth, pore-water geochemistry, and species-specific effects need to be considered in interpreting the data, our results demonstrate confidence in the use of Ba/Ca of benthic foraminifera from near-continent records as a proxy for past riverine discharge and to identify periods of drought.

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Section: Samplingmentioning

confidence: 99%

Drought recorded by Ba∕Ca in coastal benthic foraminifera

et al. 2022

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“…) (Scott & Lyons, 2012); when dissolved sulfide concentration exceeds a threshold of ∼11 μM, MoO 4 2− may be quantitatively transformed to particle-reactive MoS 4 2− (Erickson & Helz, 2000), resulting in Mo enrichment in the zone of intense SR-AOM (Jokinen et al, 2020). It is noted that sedimentary Mo enrichment is sensitive to sulfidic condition of porewater or bottom water and specific depositional/diagenetic processes involving the mechanisms of particulate Mo delivery to the sediments, and Mo recycling and burial in the sediments (Eroglu et al, 2020;Scholz et al, 2017Scholz et al, , 2018Scott & Lyons, 2012).…”

Section: Ch4 + So 2−mentioning

confidence: 99%

“…The majority of the sulfide is precipitated by reaction with dissolved Fe 2+ and/or Fe(III) oxides, initially as metastable Fe sulfides such as FeS and Fe 3 S 4 but eventually as thermodynamically stable pyrite (FeS 2 ) (Borowski et al., 2013; Peketi et al., 2012). In the sulfidic porewater conditions created by the SR‐AOM, MoO 4 2− can be readily transformed to oxythiomolybdates (MoO 4‐x S x 2− ) (Scott & Lyons, 2012); when dissolved sulfide concentration exceeds a threshold of ∼11 μM, MoO 4 2− may be quantitatively transformed to particle‐reactive MoS 4 2− (Erickson & Helz, 2000), resulting in Mo enrichment in the zone of intense SR‐AOM (Jokinen et al., 2020). It is noted that sedimentary Mo enrichment is sensitive to sulfidic condition of porewater or bottom water and specific depositional/diagenetic processes involving the mechanisms of particulate Mo delivery to the sediments, and Mo recycling and burial in the sediments (Eroglu et al., 2020; Scholz et al., 2017, 2018; Scott & Lyons, 2012).…”

Section: Introductionmentioning

confidence: 99%

Diagenetic Geochemistry of Iron, Sulfur, and Molybdenum in Sediments of the Middle Okinawa Trough Impacted by Hydrothermal Plumes and/or Cold Seeps

Qin

Zhu

Sun

et al. 2023

Earth and Space Science

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Iron (Fe), sulfur (S), and molybdenum (Mo) geochemistry in marine sediments impacted by hydrothermal plumes and/or cold seeps is complex and has not been systematically documented. Here we characterize Fe, S, and Mo diagenesis in sediments between the Minami‐Ensei Knoll hydrothermal field and a cold‐seep site of the middle Okinawa Trough. Results show that distances away from the hydrothermal field and the steep trough slope may significantly affect the transport of hydrothermal Fe. The transformation of hydrothermal reactive Fe to poorly reactive or unreactive Fe‐bearing phyllosilicates decreased the relative fractions of highly reactive Fe (FeHR) in total Fe (FeHR/FeT). Despite this, the standing stocks of Fe oxides in the methane‐free sediments have not been dampened, indicating no net impacts of hydrothermal Fe inputs on the size of Fe oxides. In the methane‐free sediments, low ratios of total reduced inorganic sulfide (TRIS) to total organic carbon (TOC) (TRIS/TOC), highly 34S‐depleted pyrite, and low Mo contents suggest that organoclastic sulfate reduction is at low rates and plays a limited role in carbon cycle. In the cold‐seep sediments, however, intense sulfate reduction coupled to anaerobic methane oxidation significantly elevate TRIS/TOC ratios, Mo enrichment, and isotope compositions of Mo and pyrite‐S. This pathway is expected to be important in carbon cycle in the basin due to the wide occurrence of cold seeps. Our results highlight the important controls of the local extreme depositional/diagenetic conditions on sedimentary S and Mo records, with implications for the reconstruction of paleoredox states of the past earth's surface.

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“…Data for GF 117 are published in Brinkmann et al (2022), and the TE sampling procedure-used for both sites-outlined therein. In short, Rhizons™ were used to collect water samples into 10-ml polyethylene syringes (Jokinen et al, 2020) at 2-cm resolution, which were subsequently transferred into centrifuge tubes and acidified (1 M HNO 3 ). The acidified BW and PW samples were analyzed for elemental concentrations of Mn, iron (Fe), sulfur (S), and Ca by inductively coupled plasma-optical emission spectrometry (ICP-OES; Thermo Scientific iCAP 6000; Helsinki University, Ecosystems and Environment Research Program) (Brinkmann et al, 2022).…”

Section: Site Descriptions and Samplingmentioning

confidence: 99%

Benthic Foraminiferal Mn/Ca as Low‐Oxygen Proxy in Fjord Sediments

Brinkmann

Barras

Jilbert

et al. 2023

Global Biogeochemical Cycles

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Fjord systems are highly vulnerable to environmental and climate changes (e.g., Bianchi et al., 2020), representing a system at the interface of terrestrial, marine, and atmospheric processes. One of the pressures aggravated by anthropogenic influences over the last century is the increase in periods of oxygen depletion observed in fjords globally (e.g., Aksnes et al., 2019;Boone et al., 2018;Jackson et al., 2021). At the same time, fjords host continuous sedimentary records, which archive Holocene environmental variability in high temporal resolution (e.g.,

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Depth and intensity of the sulfate-methane transition zone control sedimentary molybdenum and uranium sequestration in a eutrophic low-salinity setting

Cited by 15 publications

References 147 publications

Drought recorded by Ba∕Ca in coastal benthic foraminifera

Drought recorded by Ba∕Ca in coastal benthic foraminifera

Diagenetic Geochemistry of Iron, Sulfur, and Molybdenum in Sediments of the Middle Okinawa Trough Impacted by Hydrothermal Plumes and/or Cold Seeps

Benthic Foraminiferal Mn/Ca as Low‐Oxygen Proxy in Fjord Sediments

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