Modeling diffusion and reaction in soils : VIII. Gas diffusion predicted from single-potential diffusivity or permeabilty measurements
Modeling diffusion and reaction in soils : VIII. Gas diffusion predicted from single-potential diffusivity or permeabilty measurements
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模拟土壤中的扩散和反应：VIII。
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
D. Rolston
中科院分区：
文献类型：
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作者：
P. Møldrup;T. Olesen;T. Yamaguchi;P. Schjønning;D. Rolston
气体扩散系数（气体在土壤和自由空气中的扩散系数之比，Ds/Do）随土壤孔隙度（ε）的变化影响着活性气体在土壤系统中的迁移、降解和挥发。我们表明，彭曼-米林顿-夸克（PMQ）扩散率模型（在本系列的第七部分介绍）的预测精度往往是显着提高，包括作为参考点的气体扩散系数（D fc）的测量值在一个单一的土壤-水的潜力，在-100和-500 cm H2 O。结果表明，对于6种不同质地的表层土样，单次Ds/Do测量的预测均方根误差降低了45%，6 ~ 9次Ds/Do测量的平均值降低了≥ 65%。气体渗透率的测量更容易，更迅速地比气体扩散率，我们建议，在一个单一的土壤-水的潜力，结合曲折管渗透率模型和PMQ扩散率模型的气体渗透率（k fc）的测量值，也可以用来提高D s /D o的预测。为便于实际应用，本文提出了表层土在φ = -100 cm H2O时的等效管半径（rfc）与代表土壤结构形成能力的粘粒含量之间的关系。采用DARC数值模式（本系列第一部分）进行的气体扩散输运模拟验证了在Ds/Do（∈）预测中包含单个（Dfc或kfc）测量可以显著提高模拟精度。D FC和K FC为基础的扩散率模型需要有限的测量工作，并似乎有前途的气体扩散和反应的特定地点的模拟。
Variations of gas diffusivity (ratio of gas diffusion coefficients in soil and free air, D s /D o ) with air-filled porosity (∈) influence the transport, degradation, and volatilization of reactive gasses in soil systems. We show that the prediction accuracy of the Penman-Millington-Quirk (PMQ) diffusivity model (introduced in Part VII of this series) is often improved significantly by including as a reference point a measured value of the gas diffusion coefficient (D fc ) at a single soil-water potential, ψ, between -100 and -500 cm H 2 O. As a result, the root mean square error of prediction was reduced by 45% (based on individual D s /D o measurements) and by ≥ 65% (based on mean values of 6 to 9 closely-spaced D s /D o measurements) for undisturbed soil samples from six differently textured surface soils. Gas permeability is measured more easily and more rapidly than gas diffusivity, and we suggest that a measured value of gas permeability (k fc ) at a single soil-water potential, combined with a tortuous tube permeability model and the PMQ diffusivity model, can also be used to improve D s /D o predictions. For practical use, a relation between the equivalent tube radius (r fc ) at ψ = -100 cm H 2 O and clay content, taken to represent the soil structure-forming ability, is proposed for surface soils. Gas diffusive transport simulations using the DARC numerical model (Part I of this series) verified that the inclusion of a single (D fc or k fc ) measurement in the D s /D o (∈) predictions can improve simulation accuracy significantly. D fc - and k fc -based diffusivity models require limited measurement effort and seem promising for site-specific simulations of gas diffusion and reaction.