CONSTANT SLOPE IMPEDANCE FACTOR MODEL FOR PREDICTING THE SOLUTE DIFFUSION COEFFICIENT IN UNSATURATED SOIL
CONSTANT SLOPE IMPEDANCE FACTOR MODEL FOR PREDICTING THE SOLUTE DIFFUSION COEFFICIENT IN UNSATURATED SOIL
复制标题
预测不饱和土溶质扩散系数的恒斜率阻抗因子模型
DOI：
10.1097/00010694-200102000-00002
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发表时间：
2001
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：
T. Olesen;P. Møldrup;T. Yamaguchi;D. Rolston
溶质扩散系数（在土壤和自由水中的扩散系数之比，DS/D 0）明显取决于土壤类型。土壤质地和孔径分布决定了DS/D 0接近于零的临界土壤含水量（th），这是不连续扩散途径的结果。在最近的一项研究（土壤科学161：633-645）中，我们提出，可以根据基于坎贝尔孔径分布参数B的土壤-水特征曲线（SWC）预测。在这项研究中，th-b表达式进行了重新校准的基础上扩散率数据的三种土壤（广岛砂，Foulum壤土砂，和Yolo壤土）在这项研究中测量，加上20土壤在文献中报道，获得th= 0.020 b。由于土壤水稳性通常不被测量，因此第二个表达式只需要土壤质地和容重的知识就可以从测量数据中校准。第三个表达式，包括土壤质地，容重，和坎贝尔B，也进行了校准，并给出了最准确的描述。溶质阻抗因子（扩散率与土壤-水体积含量之比）f1 = DS/（D 0），随可用于扩散的水含量a= − th线性增加。大多数土壤的f1- a关系的斜率相似，没有表现出土壤类型的依赖性。在此基础上，提出了预测DS（a）/D 0的恒定斜率阻抗因子（CSIF）模型。该模型可以与三种建议表达式中的任何一种组合使用。结合土壤质地/容重依赖的表达式，该模型准确地预测溶质扩散系数为三个独立的土壤的SWC是未知的。
Solute diffusivity (ratio of diffusion coefficients in soil and free water, DS/D0) is markedly soil-type dependent. Soil texture and pore size distribution govern the threshold soil-water content (&thetas;th) where DS/D0 approaches zero as a result of discontinuous diffusion pathways. In a recent study (Soil Science 161:633-645), we suggested that &thetas;th can be predicted from the soil-water characteristic curve (SWC) based on the Campbell pore size distribution parameter, b. In this study, the &thetas;th-b expression was recalibrated based on diffusivity data for three soils (Hiroshima sand, Foulum loamy sand, and Yolo loam) measured in this study plus 20 soils reported in the literature, obtaining &thetas;th=0.020b. As the SWC is often not measured, a second &thetas;th expression that requires only knowledge of soil texture and bulk density was calibrated from measured data. A third expression, including both soil texture, bulk density, and Campbell b, was also calibrated and gave the most accurate description of &thetas;th. The solute impedance factor (ratio of diffusivity by volumetric soil-water content), f1 = DS/(&thetas; D0), was shown to increase linearly with the water content available for diffusion, &thetas;a=&thetas;−&thetas;th. The slopes of the f1-&thetas;a relations were similar for most soils and did not exhibit soil-type dependency. Based on this, a so-called constant slope impedance factor (CSIF) model to predict DS(&thetas;a)/D0 is presented. The model can be used in combination with any of the three suggested &thetas;th expressions. Combined with the soil-texture/bulk-density dependent &thetas;th expression, the model accurately predicted solute diffusivities for three independent soils for which the SWC were not known.