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  • 1
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    Stable barium isotope dynamics during estuarine mixing (2021)
    In:  EPIC3Geophysical Research Letters, ISSN: 0094-8276
    Details
    Publication Date: 2021-10-01
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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    PAPER (OA)
  • 2
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    Closing the global marine Ra-226 budget reveals the biological pump as a dominant removal flux in the upper ocean (2022)
    American Geophysical Union
    Details
    Publication Date: 2022-12-10
    Description: Author Posting. © American Geophysical Union, 2022. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 49(12), (2022): e2022GL098087, https://doi.org/10.1029/2022GL098087.
    Description: Radium isotopes are powerful proxies in oceanography and hydrology. Radium mass balance models, including assessments of submarine groundwater discharge (SGD), often overlook particle scavenging (PS) as a pathway for dissolved radium removal from the world ocean. Here, we build a global ocean 226Ra mass balance model and reevaluate the potential importance of PS. We find that PS is the major 226Ra sink for the upper ocean, removing about 96% of the total input from various sources. Aside from vertical exchange with the lower ocean, SGD is the largest 226Ra source into the upper ocean. The biological pump transfers particles to the deep ocean, resulting in a major but often overlooked impact on the global 226Ra marine budget. Our findings suggest that radium mass balance models should consider PS in systems with high siliceous algae production and export fluxes and long water residence times to prevent underestimation of large-scale SGD fluxes.
    Description: The authors are grateful to the many researchers and funding agencies responsible for the collection of data and quality control. The authors are very grateful to Jesus Gomez-Velez of Vanderbilt University for suggesting the statistical approach for distribution expansion and helping with the coding. The authors from Ocean University of China were funded by the Natural Science Foundation of China 41876075, 42130410, and 91958214, and Fundamental Research Funds for the Central Universities China 201962003 and 202072001. Funding for M.A.C. was provided by U.S. National Science Foundation OCE-1736277 and a WHOI-OUC Cooperative Research Initiative award. Valentí Rodellas acknowledges financial support from the Beatriu de Pinós postdoctoral programme of the Catalan Government (2019-BP-00241).
    Description: 2022-12-10
    Keywords: Particle scavenging ; Submarine groundwater discharge ; Siliceous algae ; Global ocean
    Repository Name: Woods Hole Open Access Server
    Type: Article
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    PAPER (OA)
  • 3
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    A benthic monitor for coastal water dissolved oxygen variation: Mn/Ca ratios in tests of an epifaunal foraminifer (2022)
    American Geophysical Union
    Details
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 126(12), (2021): e2021JC017860, https://doi.org/10.1029/2021JC017860.
    Description: An appropriate proxy could help to better understand dissolved oxygen variations in the past, helping to predict potential outcomes of future environmental changes. In the Changjiang Estuary (China), the foraminifer Cribrononion subincertum (C. subincertum) shows a distinct population maximum in the topmost sediment, an indication of an epifaunal species. Therefore, the geochemical composition of C. subincertum tests could record changes in the region’s bottom water chemistry. Our results showed that Mn/Ca ratios in tests of living (Rose-Bengal stained) C. subincertum analyzed by LA-ICP-MS were responsive to variations of bottom water dissolved oxygen concentrations, with average foraminiferal Mn/Ca ratios three times higher during low-oxygen period than in winter. In the uppermost centimeters of sediment, wider ranges of foraminiferal Mn/Ca occurred in summer compared to winter ranges. Our results imply that this epifaunal benthic foraminiferal species could serve as a useful benthic monitor with the Mn/Ca ratios representing a reliable proxy of hypoxia in the past.
    Description: This study was financially supported by the Natural Science Foundation of China (NSFC Grants 41876075, 42130410, and 41620104001), and Fundamental Research Funds for the Central Universities (201841007, 201962003, and 201961012). JMB acknowledges the Investment in Science Fund at WHOI, which supported her participation in this project.
    Description: 2022-06-17
    Keywords: Epifaunal benthic foraminifera ; Mn/Ca ratio ; Coastal hypoxia ; Proxy ; LA-ICP-MS
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
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    Simultaneous preconcentration of 9 Be and cosmogenic 10 Be for determination of the 10 Be / 9 Be ratio in (coastal) seawater (2024)
    Wiley | ASLO
    Details
    Publication Date: 2024-01-11
    Description: Beryllium isotopes have emerged as a quantitative tracer of continental weathering, but accurate and precise determination of the cosmogenic 10 Be and stable 9 Be in seawater is challenging, because seawater contains high concentrations of matrix elements but extremely low concentrations of 9 Be and 10 Be. In this study, we develop a new, time‐efficient procedure for the simultaneous preconcentration of 9 Be and 10 Be from (coastal) seawater based on the iron co‐precipitation method. The concentrations of 9 Be, 10 Be, and the resulting 10 Be/ 9 Be ratio for Changjiang Estuary water derived from the new procedure agree well with those obtained from the conventional procedure requiring separate preconcentration for 9 Be and 10 Be determinations. By avoiding the separate preconcentration, our newly developed procedure contributes toward more time‐efficient handling of samples, less sample cross‐contamination, and a more reliable 10 Be/ 9 Be ratio. Prior to this, we validated the iron co‐precipitation method using artificial seawater and natural water samples from the Amazon Estuary regarding: (1) the “matrix effect” for Be analysis, (2) its extraction efficiency for pg g −1 levels Be in the presence and absence of organic matter, and (3) the data comparability with another preconcentration method. We calculated that for the determination of 9 Be and 10 Be in most open ocean seawater with typical 10 Be concentrations of 〉 500 atoms g −1 , good precisions (〈 5%) can be achieved using less than 3 liters of seawater compared to more than 20 liters routinely used previously. Even for coastal seawater with extremely low 10 Be concentration (e.g., 100 atoms g −1 ), we estimate a maximum amount of 10 liters to be adequate.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Stable Barium Isotope Dynamics During Estuarine Mixing (2021)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2024-02-07
    Description: Stable barium isotopes are a potential proxy for riverine inputs into the ocean that reflect monsoon variability and climate change. However, dissolved Ba isotope (δ138BaDBa) geochemistry in river estuaries, a dynamic land to ocean transition zone, has rarely been systematically examined to date. Here, we show that significant Ba isotope fractionation occurs at near-zero salinities in the Yangtze and Pearl River Estuary, whereas conservative mixing dominates δ138BaDBa distributions beyond low salinities, which are well predicted by an ion exchange model. Elevated δ138BaDBa in the river endmember results from preferential removal of light Ba isotopes by adsorption to fluvial particles. Subsequently, δ138BaDBa rapidly drops to minimum signatures at increased salinities indicating particle desorption of isotopically light Ba. Nevertheless, the apparently conservative δ138BaDBa-salinity relationship beyond the low-salinity minimum in both estuaries provides a modern calibration for using Ba isotopes as a proxy for paleosalinity and river water inputs into the ocean.
    Type: Article , PeerReviewed
    Format: text
    Format: other
    Format: other
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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