Iron Reduction Controls Carbon Mineralization in Aquaculture Shrimp Pond Sediments in Subtropical Estuaries

Tan, Ji; Luo, Min; Tan, Fengfeng; Lichtfouse, Éric; Zhang, Changwei; Chen, Xin; Huang, Jiafang; Tan, Yang; Xiao, Leilei

doi:10.1029/2022jg007081

Cited by 1 publication

(1 citation statement)

References 111 publications

(145 reference statements)

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“…Recalcitrant OM is first transformed into more bioavailable substrates by ROS, and subsequently, bioavailable OM fuels Fe-reducing microbes for anaerobic respiration to enhance Fe(III) reduction when the redox condition switches to anoxic. Fe(III) reduction can account for 40–60% anaerobic respiration of OM in soils and sediments. − In addition, the remaining recalcitrant OM can be retransformed by ROS regenerated from the reduced agents in the oxidative environments. These processes back and forth alter the bioavailability of such recalcitrant OM.…”

Section: Introductionmentioning

confidence: 99%

Promotion of Humic Acid Transformation by Abiotic and Biotic Fe Redox Cycling in Nontronite

Hu,

Zeng,

Zhu

et al. 2023

Environ. Sci. Technol.

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The redox activity of Fe-bearing minerals is coupled with the transformation of organic matter (OM) in redox dynamic environments, but the underlying mechanism remains unclear. In this work, a Fe redox cycling experiment of nontronite (NAu-2), an Fe-rich smectite, was performed via combined abiotic and biotic methods, and the accompanying transformation of humic acid (HA) as a representative OM was investigated. Chemical reduction and subsequent abiotic reoxidation of NAu-2 produced abundant hydroxyl radicals (thereafter termed as ·OH) that effectively transformed the chemical and molecular composition of HA. More importantly, transformed HA served as a more premium electron donor/carbon source to couple with subsequent biological reduction of Fe(III) in reoxidized NAu-2 by Geobacter sulfurreducens, a model Fe-reducing bacterium. Destruction of aromatic structures and formation of carboxylates were mechanisms responsible for transforming HA into an energetically more bioavailable substrate. Relative to unaltered HA, transformed HA increased the extent of the bioreduction by 105%, and Fe(III) reduction was coupled with oxidation and even mineralization of transformed HA, resulting in bleached HA and formation of microbial products and cell debris. ·OH transformation slightly decreased the electron shuttling capacity of HA in bioreduction. Our results provide a mechanistic explanation for rapid OM mineralization driven by Fe redox cycling in redox-fluctuating environments.

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