How iron oxidation can direct the fate of organic matter and iron mineral composition in redox dynamic soils

Fe(II) oxidation by O₂ is an important process generating Fe (oxyhydr)oxides, which play sorptive, structural and electron-transfer roles in soils. These roles in turn can have strong implications for the fate of organic matter, particularly in redox-dynamic soils in which Fe oxidation events are quite common. Leveraging a variety of different experiments using surface and subsurface soils from the Calhoun and Luquillo Experimental Forests (formerly Critical Zone Observatories) we explore how the rate of Fe(II) oxidation (modulated by O₂ concentration), the length of Fe(II) oxidizing conditions (i.e., amount of oxic exposure), and the presence of various surfaces and organic complexing agents during Fe oxidation have implications for organic matter mineralization and composition as well as for the evolution of Fe minerals in soils. Collectively, our data suggests that while Fe reduction is often a driver of elemental release and organic matter transformation, this process is strongly influenced by the characteristics of prior Fe(II) oxidation events.

*** invited by Prof. Stefan Peiffer, Hydrology