METHANE PRODUCTION AND ITS FATE IN PADDY FIELDS .7. ELECTRON ACCEPTERS RESPONSIBLE FOR ANAEROBIC METHANE OXIDATION

Effects of electron accepters on anaerobic methane oxidation in paddy fields were investigated using a soil column. Leachate was collected periodically from the bottom of the soil column and incubated together with electron accepters (NO3-, MnO2, Fe(OH)(3), SO42-) and methane. Application of NO3- and SO42- resulted in increase of the inorganic carbon content, indicating that the activities of denitrifiers and sulfate reducers were stimulated. Methane content in the leachate decreased by the addition of MnO2 and SO42- after incubation. The amount of methane in the leachate decreased by percolation in the plow layer soil or subsoil treated with sulfurous compounds such as CaSO4, FeSO4, and elemental sulfur. These results suggested that the anaerobic oxidation of methane was associated with sulfate reduction. Analysis of SO42- content in the leachate showed that sufficient amounts of SO42- for anaerobic methane oxidation in the subsoil were leached from the plow layer soil.