277 Critical Zone Science: Intersection of Processes Linked to Geomorphology, Ecology, Fire and Climate

This session welcomes interdisciplinary studies that investigate the rates and processes of soil development, regolith formation, carbon storage and the role of ecological and/or hydrologic feedbacks in shaping the landscape (both past and present).

Wednesday, 22 October 2025
1:30 PM - 5:30 PM
HBGCC, 212AB

Arthur L. Day Medal: Coupled Redox Cycling of Iron in Clay Minerals and Organic Matter Transformation Across Redox Interfaces

Paper number: 277-2
Program: Technical Sessions
Time: 1:50 PM – 2:10 PM

Authors

Abstract

A large fraction of organic matter (OM) in soils and sediments is associated with minerals to form mineral-OM associations, which are known to decelerate OM decomposition because of protection against microbial use. However, redox cycling of Fe at redox interfaces can transform OM, yet specific pathways of coupled Fe redox cycling and OM transformation are not well understood. In this talk, I will focus on processes and mechanisms of coupled iron-carbon (Fe-C) cycles across redox interfaces [1]. Specifically, oxygenation of structural Fe(II) in minerals generates reactive oxygen species (ROS), which directly transform OM including decomposition and polymerization [2-4]. ROS also affect extracellular enzyme activity and microbial activity, thus indirectly transforming OM [5-6]. Fe(III) reduction contributes to OM oxidation through anaerobic respiration. OM plays an important role in Fe redox cycling by serving as electron donor, acceptor, shuttle, buffer, and conductor, as well as via adsorption to and coprecipitation with Fe minerals and complexation with Fe, all of which significantly alter Fe mineralogy and their reactivity [1]. Coupled Fe-C redox cycles occur in critical zone and have major implications for greenhouse gas emission, biogeochemical cycles of elements, soil fertility and food security, biodiversity and ecosystem functions, and environmental behaviour of contaminants.

References:

[1] Dong H. et al. (2023) Nat Rev Earth Environ 4:659-673.

[2] Zeng Q et al. (2019) GCA 251:136-156.

[3] Zeng Q et al (2020) Environ Sci Technol 54:15013-15023.

[4] Hu D et al (2023) Environ Sci Technol, 57:19760-19771.

[5] Dong H et al (2023) GCA 345: 102-116

[6] Sheng Y et al (2023) Environ Sci Technol 57: 3425-3433

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412128

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