A Gas Diffusion Analysis Method for Simulating Surface Nitrous Oxide Emissions in Soil Gas Concentrations Measurement
K. M. T. S. Bandara | Kazuhito Sakai | Tamotsu Nakandakari | Kozue Yuge
The detection of low gas concentrations from the soil surface demands expensive high-precision devices to estimate nitrous oxide (N<sub>2</sub>O) flux. As the prevalence of N<sub>2</sub>O concentration in the soil atmosphere is higher than its surface, the present study aimed to simulate N<sub>2</sub>O 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 (<i>D<sub>slcn</sub></i>), the measurement of the temporal variations in the N<sub>2</sub>O gas in the soil (<i>C<sub>si</sub></i>) 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 <i>C<sub>si</sub></i> and MF. Using <i>D<sub>slcn</sub></i> and <i>C<sub>si</sub></i>, the variations in the soil gas (<i>C<sub>soil</sub></i>) 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 <i>C<sub>soil</sub></i>. 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 N<sub>2</sub>O surface emissions.
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