Synchrotron X-ray microtomography (XMT) was used to measure total air-water interfacial areas (A_aw) as a function of water saturation (S_w) for several soils that comprise a range of physical and geochemical properties. Measurements were also conducted for glass beads and quartz sands for comparison. Apparent near-linear A_aw-S_w relationships are observed for the three sands and the three sandy soils. In contrast, the measured interfacial areas for two soils that contain greater proportions of silt and clay are strongly nonlinear functions of water saturation. The greater degree of nonlinearity observed for these two soils is due to their much greater particle-size distributions (i.e., uniformity coefficients) and their concomitant greater range in pore sizes. Interfacial areas determined with the thermodynamic method were used to benchmark the XMT measurements. XMT-measured interfacial areas compare well to the thermodynamic-determined values for the sands and sandy soils. In contrast, the XMT-measured interfacial areas for the two soils with larger particle-size distributions are not fully congruent with the thermodynamic-determined values. Both of these soils have large fractions of pore space comprising nominal pore diameters smaller than the resolution of the XMT imaging. These results suggest that air-water interfacial area may not always be fully characterized by standard XMT for soils with large particle-size distributions.

中文翻译：

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土壤总空气-水界面面积的显微断层扫描测量

使用同步加速器 X 射线显微断层扫描 (XMT) 来测量包含一系列物理和地球化学性质的几种土壤的总空气-水界面面积 ( A _{aw ) 作为水饱和度 (} S _w )的函数。还对玻璃珠和石英砂进行了测量以进行比较。对于三种沙子和三种沙土，观察到_明显的近线性Aw - Sw_关系。相比之下，测量的两种含有较大比例淤泥和粘土的土壤的界面面积是水饱和度的强非线性函数。对这两种土壤观察到的更大程度的非线性是由于它们更大的颗粒尺寸分布（即均匀系数）以及随之而来的更大的孔径范围。使用热力学方法确定的界面面积作为 XMT 测量的基准。 XMT 测量的界面面积与沙子和沙质土壤的热力学确定值非常吻合。相比之下，XMT 测量的两种粒径分布较大的土壤的界面面积与热力学确定的值并不完全一致。这两种土壤都具有很大一部分孔隙空间，其中包含小于 XMT 成像分辨率的标称孔径。这些结果表明，对于大粒径分布的土壤，标准 XMT 可能并不总是能完全表征空气-水界面面积。