Influence of pO 2 on Iron Redox Cycling and Anaerobic Organic Carbon Mineralization in a Humid Tropical Forest Soil

作者：Chunmei Chen, Christof Meile, Jared Wilmoth, Diego Barcellos, Aaron Thompson · 发表于：Environmental Science & Technology · 年份：2018 · DOI：10.1021/acs.est.8b01368 · 被引用次数：115 · 研究领域：Mine drainage and remediation techniques、Iron oxide chemistry and applications、Soil Carbon and Nitrogen Dynamics

Ferrous iron (Fe II ) oxidation is an important pathway for generating reactive Fe III phases in soils, which can affect organic carbon (OC) persistence/decomposition. We explored how pO 2 concentration influences Fe II oxidation rates and Fe III mineral composition, and how this impacts the subsequent Fe III reduction and anaerobic OC mineralization following a transition from oxic to anoxic conditions. We conducted batch soil slurry experiments within a humid tropical forest soil amended with isotopically labeled 57 Fe II . The slurries were oxidized with either 21% or 1% pO 2 for 9 days and then incubated for 20 days under anoxic conditions. Exposure to 21% pO 2 led to faster Fe II oxidation rates and greater partitioning of the amended 57 Fe into low-crystallinity Fe III -(oxyhydr)oxides (based on Mössbauer analysis) than exposure to 1% pO 2 . During the subsequent anoxic period, low-crystallinity Fe III -(oxyhydr)oxides were preferentially reduced relative to more crystalline forms with higher net rates of anoxic Fe II and CO 2 production—which were well correlated—following exposure to 21% pO 2 than to 1% pO 2 . This study illustrates that in redox-dynamic systems, the magnitude of O 2 fluctuations can influence the coupled iron and organic carbon cycling in soils and more broadly, that reaction rates during periods of anoxia depend on the characteristics of prior oxidation events.