Barium isotopes reveal role of ocean circulation on barium cycling in the Atlantic

Bates, Stephanie L; Hendry, Katharine R.; Pryer, Helena; Kinsley, Christopher W.; Pyle, Kimberley M.; Woodward, E. Malcolm S.; Horner, Tristan J.

doi:10.1016/j.gca.2017.01.043

Cited by 89 publications

(151 citation statements)

References 55 publications

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“…The potential role of cadmium sulfide precipitates in Cd isotope fractionation in ODZs was first proposed by Janssen et al (2014) based on (1) the observation of a Cd depletion relative to PO 4 combined with (2) an enrichment in heavy Cd isotopes in the dissolved pool, alongside (3) an enrichment in particulate Cd relative to PO 4 . The occurrence of particulate Ba in the Mauritanian ODZ due to barite precipitation supports the CdS hypothesis given that these two species are known to precipitate in similar microenvironments (S. L. Bates et al, 2017;Conway & John, 2015b;T. J. Horner et al, 2015).…”

Section: Occurrence Of Cadmium Sulfide Precipitates In the Angola Bassupporting

confidence: 65%

Importance of Cadmium Sulfides for Biogeochemical Cycling of Cd and Its Isotopes in Oxygen Deficient Zones—A Case Study of the Angola Basin

Guinoiseau

Galer

Abouchami

et al. 2019

Global Biogeochemical Cycles

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Understanding oceanic cadmium (Cd) cycling is paramount due to its micronutrient‐like behavior in seawater, which has been inferred from its similarity to phosphate (PO4) cycling. Cadmium concentrations follow a nutrient‐like consumption‐regeneration cycle in the top of the water column and are mainly controlled by water mass mixing and circulation in the deep ocean. However, an additional scavenging mechanism through cadmium sulfide (CdS) precipitates, occurring within sinking biogenic particles in oxygen deficient zones (ODZ), has been proposed. In this study, we report Cd stable isotope and concentration data for seven vertical seawater profiles sampled during GEOTRACES cruise GA08 in the northern Cape and Angola Basins, which feature a significant ODZ along their eastern margins. Outside the ODZ, Cd cycling is similar to that previously reported for the South Atlantic. While water mass mixing largely controls deep ocean Cd isotope signatures, Cd isotope fractionation in surface waters can be modeled as an open system at steady state buffered by organic ligand complexation. In the ODZ, stronger Cd depletion relative to PO4 is associated with a shift in δ114Cd toward heavier values, which is indicative of CdS precipitation. Our interpretation is supported by experimental CdS precipitation data and a size‐resolved particle model involving bacterial sulfate reduction as a precursor of CdS. Our estimates of the CdS flux to the seafloor (107 to 109 mol/yr) indicate that CdS precipitation is a significant process of Cd removal and constitutes a nonnegligible Cd sink that needs to be better quantified by Cd isotope analyses of marine sediments.

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Section: Occurrence Of Cadmium Sulfide Precipitates In the Angola Bassupporting

confidence: 65%

Importance of Cadmium Sulfides for Biogeochemical Cycling of Cd and Its Isotopes in Oxygen Deficient Zones—A Case Study of the Angola Basin

Guinoiseau

Galer

Abouchami

et al. 2019

Global Biogeochemical Cycles

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“…(), and the δ 137/134 Ba variation range of seawater is from Bates et al . (), Bridgestock et al . (), Cao et al .…”

Section: Resultsmentioning

confidence: 96%

“…This result implies that the Ba in the stalagmite may be derived from the dripping water with a homogeneous Ba isotope composition. Interestingly, the Ba isotope compositions of subsamples from the stalagmite profile (~0.34‰) were significantly heavier than the average upper continent crust (0.00 ± 0.03‰, Nan et al 2018), but similar to seawater (Cao et al 2016, Bates et al 2017, Hsieh and Henderson 2017) and corals (Pretet et al 2016, Hemsing et al 2018. This stalagmite may have inherited the Ba isotope signature of the bedrock, Triassic limestone (T 1 J), deposited in the shallow sea of the Palaeo-Tethys Ocean.…”

Section: Barium Isotopes Of Calcium Carbonate Reference Materials Andmentioning

confidence: 93%

“…Several major global rivers have d 137/134 Ba values ranging from 0.0‰ to 0.3‰ (Cao et al 2016). Ocean water profiles show systematic horizontal and depth-dependent d 137/134 Ba gradients, with surface water and open seas enriched in heavier Ba isotopes (Cao et al 2016, Bates et al 2017, Hsieh and Henderson 2017. Recently, Pretet et al (2016) used Ba isotopes in corals to explore the compositions of ambient seawater.…”

mentioning

confidence: 99%

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High‐Precision Barium Isotope Measurements of Carbonates by MC‐ICP‐MS

Zeng

Liu

et al. 2019

Geostandard Geoanalytic Res

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This study presents a high‐precision method to measure barium (Ba) isotope compositions of international carbonate reference materials and natural carbonates. Barium was purified using chromatographic columns filled with cation exchange resin (AG50W‐X12, 200–400 mesh). Barium isotopes were measured by MC‐ICP‐MS, using a 135Ba–136Ba double‐spike to correct mass‐dependent fractionation during purification and instrumental measurement. The precision and accuracy were monitored by measuring Ba isotope compositions of the reference material JCp‐1 (coral) and a synthetic solution obtained by mixing NIST SRM 3104a with other matrix elements. The mean δ137/134Ba values of JCp‐1 and the synthetic solution relative to NIST SRM 3104a were 0.21 ± 0.03‰ (2s, n = 16) and 0.02 ± 0.03‰ (2s, n = 6), respectively. Replicate measurements of NIST SRM 915b, COQ‐1, natural coral and stalagmite samples gave average δ137/134Ba values of 0.10 ± 0.04‰ (2s, n = 18), 0.08 ± 0.04‰ (2s, n = 20), 0.27 ± 0.04‰ (2s, n = 16) and 0.04 ± 0.03‰ (2s, n = 20), respectively. Barium mass fractions and Ba isotopes of subsamples drilled from one stalagmite profile were also measured. Although Ba mass fractions varied significantly along the profile, Ba isotope signatures were homogeneous, indicating that Ba isotope compositions of stalagmites could be a potential tool (in addition to Ba mass fractions) to constrain the source of Ba in carbonate rocks and minerals.

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“…Specifically, particulate “excess Ba” (Ba xs i.e., any Ba that is present in particles that is unsupported by lithogenic material) correlates with the flux of particulate organic carbon (POC) measured in suspended particulates (Dehairs et al, ; Thomas et al, ), sediment traps (Cardinal et al, ), and seafloor sediments (Eagle et al, ). More recent studies, including those utilizing marine barium isotopes, also highlight the nonconservative behavior of barium in near surface waters (Bates et al, ; Horner et al, ; Hsieh & Henderson, ; Jullion et al, ).…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal Variability of Barium in Arctic Sea‐Ice and Seawater

et al. 2018

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Freshwater export from the Arctic is critical in determining the density of water at sites of North Atlantic deep water formation, which in turn influences the global flux of oceanic heat and nutrients. We need geochemical tracers and high-resolution observations to refine our freshwater budgets and constrain models for future change. The use of seawater barium concentrations in the Arctic Ocean as a freshwater tracer relies on the conservative behavior of barium in seawater; while this has been shown to be an unreliable assumption in Arctic summers, there are a lack of studies observing seasonal progressions. Here, we present barium concentrations from seawater and sea-ice collected during the Norwegian Young Sea ICE expedition from boreal winter into summer. We use other tracers (salinity, oxygen isotopes, and alkalinity) to reconstruct freshwater inputs and calculate a barium ''deficit'' that can be attributed to nonconservative processes. We locate a deficit in winter when biological production is low, which we attribute to uptake by barite formation associated with old organic matter or by internal sea-ice processes. We also find a significant barium deficit during the early spring bloom, consistent with uptake into organic-matter associated microenvironments. However, in summer, there no strong barium deficit near the surface, despite high biological production and organic carbon standing stocks, perhaps reflecting phytoplankton assemblage changes, and/or rapid internal cycling. Our findings challenge the assumptions surrounding the use of barium as an Arctic freshwater tracer, and highlight the need to improve our understanding of barium in sea-ice environments.

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Barium isotopes reveal role of ocean circulation on barium cycling in the Atlantic

Cited by 89 publications

References 55 publications

Importance of Cadmium Sulfides for Biogeochemical Cycling of Cd and Its Isotopes in Oxygen Deficient Zones—A Case Study of the Angola Basin

Importance of Cadmium Sulfides for Biogeochemical Cycling of Cd and Its Isotopes in Oxygen Deficient Zones—A Case Study of the Angola Basin

High‐Precision Barium Isotope Measurements of Carbonates by MC‐ICP‐MS

Spatiotemporal Variability of Barium in Arctic Sea‐Ice and Seawater

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