Two-Region Extended Archie's Law Model for Soil Air Permeability and Gas Diffusivity
Two-Region Extended Archie's Law Model for Soil Air Permeability and Gas Diffusivity
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DOI：
10.2136/sssaj2010.0207
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发表时间：
2011-05
影响因子：
2.9
通讯作者：
S. Hamamoto;P. Møldrup;K. Kawamoto;L. W. Jonge;P. Schjønning;T. Komatsu
中科院分区：
文献类型：
--
作者：
S. Hamamoto;P. Møldrup;K. Kawamoto;L. W. Jonge;P. Schjønning;T. Komatsu
空气渗透率 (ka ) 和土壤气体扩散系数 (D p ) 是不同饱和土壤中气体传输和归宿的控制因素。我们基于经典阿尔奇定律开发了 k a 和 D 的统一模型，并扩展为：（i）允许结构化土壤的两区域气体传输行为，以自然场湿度条件（设置为 -100 cm H 2 O 基质势 [pF 2]）作为大孔隙（pF ≤ 2 时排水孔径≥30 μm）和小孔隙（随后排水孔隙）之间的参考（拼接）点2) 区域，以及 (ii) 包括渗滤阈值，对于无结构多孔介质，设置为总孔隙度的 10%；对于结构化土壤，设置为大孔隙区域孔隙度的 10%。由此产生的带有参考点 (EXAR) 模型的扩展阿奇定律 k a 和 D 适合测量数据。对于无结构和结构化多孔介质，D p 的阿奇饱和指数 (n) 高于 k a ，表明水阻塞对气体扩散的影响更大。对于结构化土壤，大孔隙区域的饱和指数 (n 1 ) 低于小孔隙区域的饱和指数 (n 2 )。一般来说，k a 的 n 1 值约为 1，D p 的 n 2 值约为 2，k a 的 n 2 值分别为 4/3 和 D 的 7/3，可以很好地描述数据。还开发了 pF 2 处 k a 的两个参考点表达式，并与 pF 2 处 D 的现有模型一起针对不同土壤类型的独立数据进行了测试。性能最佳的参考点模型是基于经典 Kozeny 方程和 Moldrup D p 模型的 k a 模型。
The air permeability (k a ) and soil gas diffusion coefficients (D p ) are controlling factors for gas transport and fate in variably saturated soils. We developed a unified model for k a and D based on the classical Archie's law, extended by: (i) allowing for two-region gas transport behavior for structured soils, with the natural field moisture condition (set at -100 cm H 2 O matric potential [pF 2]) as the reference (spliced) point between the large-pore (drained pore diameter ≥30 μm at pF ≤ 2) and the small-pore (subsequently drained pores 2) regions, and (ii) including a percolation threshold, set as 10% of the total porosity for structureless porous media or 10% of the porosity in the large-pore region for structured soils. The resulting extended Archie's law with reference point (EXAR) models for k a and D were fitted to the measured data. For both structureless and structured porous media, Archie's saturation exponent (n) was higher for D p than for k a , indicating higher water blockage effects on gas diffusion. For structured soils, the saturation exponent for the large-pore region (n 1 ) was lower than for the small-pore region (n 2 ). Generally, n 1 values of ∼1 for k a and 2 for D p and n 2 values of 4/3 for k a and 7/3 for D described the data well. Two reference-point expressions for k a at pF 2 were also developed and tested together with existing models for D at pF 2 against independent data across soil types. The best-performing reference-point models were a k a model based on the classical Kozeny equation and the Moldrup D p model.