Organic Matter Fraction Dependent Model for Predicting the Gas Diffusion Coefficient in Variably Saturated Soils
Organic Matter Fraction Dependent Model for Predicting the Gas Diffusion Coefficient in Variably Saturated Soils
复制标题
DOI：
10.2136/vzj2011.0065
复制
发表时间：
2012-02
影响因子：
2.8
通讯作者：
S. Hamamoto;P. Møldrup;K. Kawamoto;T. Komatsu
中科院分区：
文献类型：
--
作者：
S. Hamamoto;P. Møldrup;K. Kawamoto;T. Komatsu
气体扩散是气层内气候和调节气体的主要输运机制。土壤-气体扩散受气体扩散系数（Dp, m2 s−1）控制，该系数高度依赖于土壤质地，如沙子、淤泥、粘土和有机质含量，以及土壤物理性质，如土壤-空气含量（ε, m3 m−3）或总孔隙度（Φ， m3 m−3）。土壤有机质是土壤孔隙结构（即总孔隙度和充满空气的孔隙弯曲度）形成的关键因素，它对变饱和条件下的Dp行为有很大影响。在本研究中，基于砂、壤土、火山灰土和有机土等土壤类型的大量Dp数据集，提出了包含渗流阈值（εth, m3 m−3）和孔隙扭曲系数（X′）的预测Dp模型。观测到的εth或X′与Φ或体积有机质分数（OMF, m3 m−3）之间的关系嵌入到所提出的Dp模型中。该模型与预测ε - th和OMF模型相结合，对不同土壤类型的Dp实测数据具有较好的拟合效果。最后，对OMF对Dp和孔网扭曲度(T)的敏感性分析表明，在相同的ε条件下，随着OMF的增加，Dp降低，T增加。
Gas diffusion is a dominant transport mechanism for climate and regulated gases in the vadose zone. Soil‐gas diffusion is governed by the gas diffusion coefficient (Dp, m2 s−1) which is highly dependent on soil texture, such as sand, silt, clay, and organic matter contents, as well as soil physical properties such as soil‐air content (ε, m3 m−3) or total porosity (Φ, m3 m−3). Soil organic matter is a key contributor to the formation of the soil pore structure (i.e., total porosity and air‐filled pore tortuosity), and it highly affects Dp behavior under variably saturated conditions. In this study, based on numerous Dp data sets across soil types including sands, loamy clay soils, volcanic ash soils, and organic soils, predictive Dp models incorporating a percolation threshold (εth, m3 m−3) and pore tortuosity factor (X′) are proposed. The observed relations between either εth or X′ and either Φ or volumetric organic matter fraction (OMF, m3 m−3) were embedded in the proposed Dp model. The proposed Dp models, coupled with predictive εth and OMF models, performed well against the measured Dp data across soil types. Finally, a sensitivity analysis of the OMF in relation to the Dp and pore‐network tortuosity (T) showed a reduction in Dp and increase in T with increasing OMF under the same ε conditions.