ORIGINAL

Abstract

Wetlands are the largest natural source of methane (CH4) on the planet, but the mechanisms by which compositional differences in wetland soil and temporal variations in hydrology affect CH4 production are poorly understood. Incubations of peat collected from a temperate bog have shown that, after exposure to O2, CH4 production increased during subsequent anoxia relative to soil which was kept anoxic. We incubated all potential combinations of fully anoxic or transiently oxic and unamended or ferric oxyhydroxide (FeOOH·nH2O)-amended marsh soil from the Charles H. Rogers Wildlife Refuge, NJ in order to investigate whether post-oxic amplified CH4 production also occurs in marsh soil, and to evaluate the effectiveness of ferric iron addition as a CH4 mitigation method. We find that transient O2 exposure delays the onset of marsh soil CH4 production and reduces the total CH4 produced, while the FeOOH·nH2O addition reduces CH4 and CO2 production regardless of O2 exposure, and thus shows promise as a CH4 mitigation technique. While the COVID-19 pandemic prevented the collection of genetic, chemical, and mineral data for the incubations, we suspect that these responses are related to changes in soil organic carbon availability (either through depletion during previous oxygenation events or mineral protection) and/or direction inhibition of soil microorganisms by O2 or FeOOH·nH2O.