Impact of estuaries on fluvial Cr input into the ocean: Perspectives from the Mobile Bay Estuary, Northern Gulf of Mexico

Mallick, Debbrota; Wang, Xiangli; Beebe, Donald A.

doi:10.1016/j.gca.2022.08.004

Cited by 5 publications

(1 citation statement)

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“…The Cr budget in modern oceans has been reviewed previously (Qin & Wang, 2017; Reinhard et al., 2013; Wei et al., 2018, 2020). Rivers are considered the main source of Cr into the ocean (Reinhard et al., 2013), with mostly positive δ 53 Cr values ranging from −0.17 to 1.68‰ (D'Arcy et al., 2016; Goring‐Harford et al., 2020; Mallick et al., 2022; Sun et al., 2019; Wu et al., 2017). Oxic, hypoxic, and anoxic sediments and carbonates are the main sinks of Cr in oceans (Wei et al., 2020).…”

Section: Introductionmentioning

confidence: 99%

Stable Chromium Isotope Fractionation During the Alteration of Abyssal Peridotite: Implications for Marine Chromium Isotope Mass Balance

Liu,

Xu,

et al. 2024

JGR Solid Earth

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The stable chromium isotope system has been widely used as a redox proxy to reconstruct the oxygenation history of ocean atmosphere systems. However, the Cr isotope mass balance in modern oceans (i.e., inputs and outputs) remains poorly constrained. To investigate the influence of seawater‐peridotite reaction on the global marine Cr isotope mass balance, we report high‐precision Cr isotope data (δ53Cr) on a series of fresh and altered abyssal peridotites from the Gakkel Ridge and the Southwest Indian Ridge (SWIR). The least altered peridotites give a δ53Cr value of −0.08 ± 0.06‰ (2SD, n = 4) for the oceanic mantle which is consistent with the established δ53Cr of the Bulk Silicate Earth. Compared to fresh peridotites, a subset of altered peridotites exhibit a loss of isotopically light Cr with relatively positive δ53Cr values (up to 0.04‰). These altered peridotites are characterized by significant Cr loss and likely have been subject to serpentinization. By contrast, seafloor weathering has limited influence on the Cr concentrations and isotopic compositions of the altered peridotites. Monte Carlo (MC) simulations of marine alteration suggest a net Cr flux into seawater from altered abyssal peridotites of ∼3.5 × 108 mol/yr, which is on the same order of magnitude as the riverine input flux of 108–109 mol/yr. Furthermore, the MC results suggest that the peridotite‐sourced net Cr flux has a negative δ53Cr signature (−0.33 ± 0.21‰, 2SD). Thus, seawater‐peridotite interactions must be considered when evaluating the modern oceanic Cr isotope mass balance.

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