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Huang T, Moos SB, Boyle EA. Trivalent chromium isotopes in the eastern tropical North Pacific oxygen-deficient zone. Proc Natl Acad Sci U S A. 2021;118(8)doi: 10.1073/pnas.1918605118.
Huang, T., Moos, S. B., & Boyle, E. A. (2021). Trivalent chromium isotopes in the eastern tropical North Pacific oxygen-deficient zone. Proceedings of the National Academy of Sciences of the United States of America, 118(8), . https://doi.org/10.1073/pnas.1918605118
Huang, Tianyi, et al. "Trivalent chromium isotopes in the eastern tropical North Pacific oxygen-deficient zone." Proceedings of the National Academy of Sciences of the United States of America vol. 118,8 (2021). doi: https://doi.org/10.1073/pnas.1918605118
Huang T, Moos SB, Boyle EA. Trivalent chromium isotopes in the eastern tropical North Pacific oxygen-deficient zone. Proc Natl Acad Sci U S A. 2021 Feb 23;118(8). doi: 10.1073/pnas.1918605118. PMID: 33602803; PMCID: PMC7923599.
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Proc Natl Acad Sci U S A. 2021 Feb 23;118(8). doi: 10.1073/pnas.1918605118.

Trivalent chromium isotopes in the eastern tropical North Pacific oxygen-deficient zone.

Proceedings of the National Academy of Sciences of the United States of America

Tianyi Huang, Simone B Moos, Edward A Boyle

Affiliations

  1. Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139.
  2. Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program in Oceanography, Cambridge, MA 02139.
  3. Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139; [email protected].

PMID: 33602803 PMCID: PMC7923599 DOI: 10.1073/pnas.1918605118

Abstract

Changes in chromium (Cr) isotope ratios due to fractionation between trivalent [Cr(III)] and hexavalent [Cr(VI)] are being utilized by geologists to infer oxygen conditions in past environments. However, there is little information available on Cr in the modern ocean to ground-truth these inferences. Transformations between the two chromium species are important processes in oceanic Cr cycling. Here we present profiles of hexavalent and trivalent Cr concentrations and stable isotope ratios from the eastern tropical North Pacific (ETNP) oxygen-deficient zone (ODZ) which support theoretical and experimental studies that predict that lighter Cr is preferentially reduced in low-oxygen environments and that residual dissolved Cr becomes heavier due to removal of particle-reactive Cr(III) on sinking particles. The Cr(III) maximum dominantly occurs in the upper portion of the ODZ, implying that microbial activity (dependent on the sinking flux of organic matter) may be the dominant mechanism for this transformation, rather than a simple inorganic chemical conversion between the species depending on the redox potential.

Keywords: chromium isotopes; hexavalent chromium; oxygen-deficient zones; trace elements; trivalent chromium

Conflict of interest statement

The authors declare no competing interest.

References

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