The marine biogeochemistry of chromium isotopes

Moos, Simone Beatrice

doi:10.1575/1912/9489

Cited by 4 publications

(14 citation statements)

References 77 publications

(105 reference statements)

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“…A compilation of OMZ data (colored symbols in Figure ) shows a more complex relationship between Cr concentration and δ 53 Cr. Total Cr isotope data from ETNP suboxic seawater profiles (Moos, ; Moos & Boyle, ) are consistent with the Rayleigh‐type line observed in Scheiderich et al (). However, total seawater δ 53 Cr data from the eastern Atlantic OMZ by Goring‐Harford et al (), and species‐specific δ 53 Cr data from ETNP reported by this study, only partially fall on the linear trend.…”

Section: Discussionsupporting

confidence: 84%

“…Given more than a 2,400‐mile distance between these locations, such difference in δ 53 Cr may be explained by the highly heterogeneous distribution of Cr isotopes in the modern ocean. In addition, Moos () reported Cr concentration (2.27–3.21 nM) and δ 53 Cr (0.99–1.19‰) at the same station 2 and another station near our station 10 (station 7T in Moos, ), which are both lower than our values (2.37–2.58 nM Cr (VI) at station 2 and 4.6–5.27 nM total dissolved Cr at station 10). Moos () samples and our samples were collected 1 year apart (June 2013 for our samples and May 2014 for Moos, ).…”

Section: Discussioncontrasting

confidence: 75%

“…The color bar represents the δ 53 Cr value of surface seawater (≤100 m). Literature data sources: Bonnand et al (), Frei et al (), Paulukat et al (), Pereira et al (), Scheiderich et al (), D'Arcy et al (), Economou‐Eliopoulos et al (), Holmden et al (), Paulukat et al (), Goring‐Harford et al (), Moos (), and Moos and Boyle ().…”

Section: Discussionunclassified

“…The map shows station locations where depth profile δ 53 Cr data are available. Literature data sources: Bonnand et al (), Scheiderich et al (), Goring‐Harford et al (), Moos (), Moos and Boyle (), and Sun et al (). ConRiverEst = the Connecticut River estuary, III = Cr (III), VI = Cr (VI), tot = total Cr.…”

Section: Discussionmentioning

confidence: 99%

“…Correlations between Cr concentration and dissolved O 2 concentration (a, c, e) and between δ 53 Cr and dissolved O 2 concentration (b, d, f) under oxic (ox: O 2 ≥4 μM) and suboxic (subox: O 2 ≥4 μM) conditions. Literature data sources for Cr concentration (1,075 data points) and δ 53 Cr (92 data points) that have accompanied dissolved O 2 data (Cranston, ; Emerson et al, ; Goring‐Harford et al, ; Jeandel & Minster, ; Moos, ; Moos & Boyle, ; Rue et al, ; Scheiderich et al, ). In Figure h, the left y axis is for oxic‐total, whereas the right y axis is for all other data.…”

Section: Discussionmentioning

confidence: 99%

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Species‐Dependent Chromium Isotope Fractionation Across the Eastern Tropical North Pacific Oxygen Minimum Zone

Wang

Glass

Reinhard

et al. 2019

Geochem Geophys Geosyst

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The stable chromium (Cr) isotope system is an emerging paleoredox proxy. Interpretation of sedimentary and seawater δ53Cr (53Cr/52Cr relative to SRM 979) hinges on our understanding of the isotopic fractionations during Cr sequestration from seawater to sediments. Seawater δ53Cr values reported thus far are for total dissolved Cr. This study reports the δ53Cr of both dissolved Cr (III) and dissolved Cr (VI) across the oxygen minimum zone in the eastern tropical North Pacific off Manzanillo, Mexico. Dissolved Cr (III) accounts for 48% to 54% total dissolved Cr in this region. There are no correlations between O2 and Cr concentrations, or O2 concentrations and δ53Cr throughout the water column. The δ53Cr of Cr (III) is lower than that of Cr (VI) by a relatively constant offset (0.42 ± 0.15‰, 1σ, n = 5) and is also uncorrelated with dissolved O2 concentration. These observations provide part of the foundation for using δ53Cr of the authigenic Cr in organic‐rich shales to reconstruct seawater δ53Cr. A survey of growing literature Cr concentration and δ53Cr data suggests that the Cr isotope fractionation factor in the global ocean is likely more complex than previously thought. More future species‐dependent Cr isotope studies could shed new light on the biogeochemical processes controlling the oceanic Cr isotope fractionation.

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Section: Discussionsupporting

confidence: 84%

Section: Discussioncontrasting

confidence: 75%

Section: Discussionunclassified

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Species‐Dependent Chromium Isotope Fractionation Across the Eastern Tropical North Pacific Oxygen Minimum Zone

Wang

Glass

Reinhard

et al. 2019

Geochem Geophys Geosyst

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Chromium isotope cycling in the water column and sediments of the Peruvian continental margin

Bruggmann

Scholz

Klaebe

et al. 2019

Geochimica et Cosmochimica Acta

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Chromium (Cr) isotope fractionation is sensitive to redox changes and the Cr isotopic composition (δ 53 Cr) of sedimentary rocks has been used to reconstruct marine redox conditions and atmospheric oxygenation in the past. However, little is known about the behaviour of chromium isotopes across modern marine redox boundaries. We investigated Cr concentrations and δ 53 Cr variations in seawater and sediment across the Peruvian oxygen minimum zone (OMZ) to provide a better understanding of Cr cycling in the ocean. We found that seawater δ 53 Cr values ranged from 0.02 ± 0.16 ‰ to 0.59 ± 0.11 ‰ (2SD) and sediment values from 0.31 ± 0.07 to 0.92 ± 0.12 ‰. Neither Cr concentrations nor δ 53 Cr values in the water column revealed significant shifts across the oxic-anoxic boundaries. Instead, processes that operate at a local scale, such as Cr scavenging by Fe-rich particles and Cr release from reducing sediments, are identified as the main controls on Cr concentrations and isotope compositions in the water column. The δ 53 Cr values of sediments deposited in permanently anoxic waters (0.77 ± 0.19 ‰, n = 5) are significantly different from the δ 53 Cr values of sediments deposited in oxic bottom waters (0.46 ± 0.19 ‰, n = 4). This suggests that sediment Cr concentrations and δ 53 Cr values are to some extent influenced by water column redox (e.g. reductive dissolution and transport of Fe oxides) and/or early diagenetic (e.g. redistribution of Cr during phosphogenesis) processes as well as biologic activity. Our data demonstrate that local scale water column redox gradients and sediment exchange can lead to a large range of δ 53 Cr values in sediments, comparable to the range found in the entire geologic record to date.Given the increasing prominence of Cr isotope measurements in constraining atmospheric oxygenation in deep time, we argue that the processes influencing Cr cycling under different conditions and from the water column to the sediment need to be better resolved to verify the utility of such measurements as paleoenvironmental proxies.

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Shelf-to-basin shuttle of highly fractionated chromium isotopes in the Arctic Ocean

Baconnais,

Holmden

2024

Geochimica et Cosmochimica Acta

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The marine biogeochemistry of chromium isotopes

Cited by 4 publications

References 77 publications

Species‐Dependent Chromium Isotope Fractionation Across the Eastern Tropical North Pacific Oxygen Minimum Zone

Species‐Dependent Chromium Isotope Fractionation Across the Eastern Tropical North Pacific Oxygen Minimum Zone

Chromium isotope cycling in the water column and sediments of the Peruvian continental margin

Shelf-to-basin shuttle of highly fractionated chromium isotopes in the Arctic Ocean

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