A new apparatus for measuring the gas diffusion coefficient in soil using a large sample and controlling soil water suction

A new apparatus that determines the gas diffusion coefficient in soil after establishing steady state gas conditions was developed. The CO₂ concentration is kept constant above and below the soil sample to establish the steady state conditions. The sample column is 60 cm long with an inner diameter of 20 cm. The gas diffusion coefficients of sandy soil were measured at 10 cm intervals using this apparatus while controlling the soil water content. The ratios of gas diffusion coefficients in soil and air,D _s/D₀, with different soil water conditions were determined. A part of this paper was presented at the 110th Annual Meeting of the Japanese Forestry Society (1999).