A Gas Diffusion Analysis Method for Simulating Surface Nitrous Oxide Emissions in Soil Gas Concentrations Measurement
2022
Bandara, K. M. T. S. | Sakai, Kazuhito | Nakandakari, Tamotsu | Yuge, Kozue
The detection of low gas concentrations from the soil surface demands expensive high-precision devices to estimate nitrous oxide (N₂O) flux. As the prevalence of N₂O concentration in the soil atmosphere is higher than its surface, the present study aimed to simulate N₂O surface flux (CF) from soil gas measured in a soil-interred silicone diffusion cell using a low-cost device. The methodological steps included the determination of the diffusion coefficient of silicone membrane (Dₛₗcₙ), the measurement of the temporal variations in the N₂O gas in the soil (Cₛᵢ) and on the surface (MF), and the development of a simulation process for predicting CF. Two experiments varying the procedure and periods of soil moisture saturation in each fertilized soil sample were conducted to detect Cₛᵢ and MF. Using Dₛₗcₙ and Cₛᵢ, the variations in the soil gas (Cₛₒᵢₗ) were predicted by solving the diffusion equation using the implicit finite difference analysis method. Similarly, using six soil gas diffusivity models, the CF values were simulated from Cₛₒᵢₗ. For both experiments, statistical tests confirmed the good agreement of CF with MF for soil gas diffusivity models 4 and 5. We suggest that the tested simulation method is appropriate for predicting N₂O surface emissions.
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