[A-GE27] Subsurface Mass Transport and Environmental Assessment

[AGE27-P11] Effects of Artificial Macropore Application to Paddy Soil on Redox Potential and its Relation to Iron and Manganese Leaching

*Kota Hamaoka¹, Long Thanh Bui¹, Yasushi Mori¹ (1.Graduate School of Environmental and Life Science, Okayama University)

Keywords:artificial macropore, iron, manganese, redox potential, methane

Paddy fields are big sources of methane gas which contributes to global warming. Methane emission is enhanced in the reducing condition. Macropores in paddy fields may work as pathways of oxygen and lighten the reducing condition. However, the relationship between soil structure, redox potential, and methane gas emissions is unclear. In this research, we tried to understand how macropores affect to the paddy fields’ condition. We prepared four types of columns: with drainage with macropore, with drainage without macropore, no drainage with macropore, and no drainage without macropore. We measured pH, redox potential, soil height, surface water depth, soil moisture, CO2 and CH4 concentration in the columns, and ICP measurement of iron and manganese dissolved in drained water in the column for 30 days. CO2 and CH4 emissions increased with the application of artificial macropores. Whereas the application of the artificial macropore was capable of keeping the redox potential as high as the application of drainage. The leaching concentrations of iron and manganese were 5.48 mg/l and 0.375 mg/l, respectively, in the drained water of the column with drainage without macropore. The drained water of the column with drainage with macropore contained iron and manganese 4.87 mg/l and 0.322 mg/l. It showed that applying artificial macropore restrained both iron and manganese leaching because artificial macropore kept redox potential higher.