Gas diffusion coefficient in variably saturated peat soil: Measurements and test of prediction models

摘要

The soil-gas diffusion coefficient (D_p) and its dependency on air-filled porosity (ε) govern the gas diffusion and reaction processes in soil. Accurate D_p (ε) prediction models for variably saturated peat soils are needed to evaluate vadose zone transport and fate of greenhouse gases such as methane in peaty wetlands. In this study, we measured D_p on peat soil samples at different soil-water matric potentials, and developed new, linear and nonlinear expressions for describing and predicting D_p (ε). Undisturbed peat soil samples were taken from Bibai wetland, Hokkaido, Japan. By modifying 3 existing D_p (ε) models, the Buckingham model, the Macroporosity-Dependent model, and the Penman-Call model, we suggested 3 new D_p (ε) models for peat soils. To validate the new D_p (ε) models, we tested the models against independent datasets for peat soil samples from literatures. The modified Buckingham type model performed the best against independent datasets.