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<p>The highly reactive iron (Fe<sub>HR</sub>) in marine sediments is a key driver of the iron-carbon coupled biogeochemical cycle. However, rare is known on its speciation and environmental regulation mechanisms in the climate-sensitive West Antarctic region. This study investigated the spatial distribution of Fe<sub>HR</sub> content and composition in surface sediments of the Ross Sea, examined the synergistic regulatory mechanisms of chemical weathering intensity (quantified by the chemical index of alteration, CIA), bedrock properties and glacial meltwater input on Fe<sub>HR</sub> characteristics, and elucidated the interaction between Fe<sub>HR</sub> and total organic carbon (TOC), and its implications for the sedimentary environment. Basically, the CIA (52.7±1.46) and Fe<sub>HR</sub>/Fe<sub>T</sub> ratio (0.20±0.02) are higher in the eastern Ross Sea than the western (45.4±2.73 and 0.17±0.01), probably resulting from the selective enrichment of fine-grained materials subjected to intense chemical weathering under low sedimentation rates. Interestingly, the CIA (37.6±5.45) is lowest, but Fe<sub>HR</sub>/Fe<sub>T</sub> ratio (0.25±0.01) is highest in the southwestern Ross Sea, mainly due to igneous bedrock, katabatic winds and glacial meltwater input in a weakly weathered environment. Relative high TOC/Fe<sub>HR</sub> ratios (1.29±0.30 and 1.04±0.70) in the southwestern and western Ross Sea indicate a sedimentary environment with high primary production and exogenous Fe<sub>HR</sub> inputs. While, relative low TOC/Fe<sub>HR</sub> ratio (0.63±0.13) in the eastern Ross Sea indicates the dual control of strong TOC remineralization and intense chemical weathering-derived Fe<sub>HR</sub> production. The chemical weathering intensity is the primary controlling factor for Fe<sub>HR</sub> content and composition in marine sediments globally, according to the significant positive correlations between Fe<sub>HR</sub>/Fe<sub>T</sub> ratios and CIA values (<i>r</i>=0.80) as well as Fe<sub>T</sub> content (<i>r</i>=0.57). The unique glacial meltwater and lithological characteristics of the Antarctic region can significantly influence local Fe<sub>HR</sub>/Fe<sub>T</sub> ratio, thereby regulating bioavailable Fe supply and TOC preservation. This finding provides new regional constraints for understanding iron-carbon coupling processes in polar regions.</p>

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Highly reactive iron in Ross Sea surface sediments: Spatial heterogeneity, environmental controls and implications for Antarctic shelf deposition

  • 期刊论文

  • 发表日期：

    2025年6月23日

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  • Wenhao Huang,
  • Jun Zhao,
  • Xiaoze Guo,
  • Dong Li,
  • Ji Hu,
  • Haifeng Zhang,
  • Changfeng Zhu,
  • Jianming Pan,
  • Jianfang Chen

摘要

The highly reactive iron (FeHR) in marine sediments is a key driver of the iron-carbon coupled biogeochemical cycle. However, rare is known on its speciation and environmental regulation mechanisms in the climate-sensitive West Antarctic region. This study investigated the spatial distribution of FeHR content and composition in surface sediments of the Ross Sea, examined the synergistic regulatory mechanisms of chemical weathering intensity (quantified by the chemical index of alteration, CIA), bedrock properties and glacial meltwater input on FeHR characteristics, and elucidated the interaction between FeHR and total organic carbon (TOC), and its implications for the sedimentary environment. Basically, the CIA (52.7±1.46) and FeHR/FeT ratio (0.20±0.02) are higher in the eastern Ross Sea than the western (45.4±2.73 and 0.17±0.01), probably resulting from the selective enrichment of fine-grained materials subjected to intense chemical weathering under low sedimentation rates. Interestingly, the CIA (37.6±5.45) is lowest, but FeHR/FeT ratio (0.25±0.01) is highest in the southwestern Ross Sea, mainly due to igneous bedrock, katabatic winds and glacial meltwater input in a weakly weathered environment. Relative high TOC/FeHR ratios (1.29±0.30 and 1.04±0.70) in the southwestern and western Ross Sea indicate a sedimentary environment with high primary production and exogenous FeHR inputs. While, relative low TOC/FeHR ratio (0.63±0.13) in the eastern Ross Sea indicates the dual control of strong TOC remineralization and intense chemical weathering-derived FeHR production. The chemical weathering intensity is the primary controlling factor for FeHR content and composition in marine sediments globally, according to the significant positive correlations between FeHR/FeT ratios and CIA values (r=0.80) as well as FeT content (r=0.57). The unique glacial meltwater and lithological characteristics of the Antarctic region can significantly influence local FeHR/FeT ratio, thereby regulating bioavailable Fe supply and TOC preservation. This finding provides new regional constraints for understanding iron-carbon coupling processes in polar regions.