Measuring air-water interfacial areas with X-ray microtomography and interfacial partitioning tracer tests
Measuring air-water interfacial areas with X-ray microtomography and interfacial partitioning tracer tests
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DOI：
10.1021/es061474m
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发表时间：
2007-03-15
影响因子：
11.4
通讯作者：
Murao, Asami
中科院分区：
文献类型：
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作者：
Brusseau, Mark L.;Peng, Sheng;Murao, Asami
使用两种方法，即水相界面分配示踪剂测试和同步加速器 X 射线显微断层扫描，测量了沙质天然多孔介质的空气-水界面面积与水饱和度的函数关系。此外，还包括先前研究中使用气相界面分配示踪剂测试方法对相同多孔介质测量的界面面积以进行比较。对于所有三种方法，总空气-水界面面积随着水饱和度的降低而增加。用示踪剂测试方法测量的界面面积通常大于显微断层扫描获得的界面面积，并且随着水饱和度的降低，差异增大。通过显微断层扫描测量的界面面积外推到与使用光滑球假设计算的固体比表面积（151 cm(-1)）非常相似的值（147 cm(-1)），表明该方法不能表征与微观表面异质性（表面粗糙度、微孔隙率）相关的面积。这与大约 12 μm 的方法分辨率一致。相比之下，气相示踪剂测试测量的界面面积接近N-2/BET测量的比固体表面积（56 000 cm(-1)），表明该方法确实表征了与微观表面异质性相关的界面面积。水相示踪剂测试测得的最大界面面积为224 cm(-1)，而外推最大界面面积约为1100 cm(-1)。这两个值均大于光滑球体比固体表面积，但远小于 N-2/BET 比固体表面积，这表明该方法测量与微观表面异质性相关的界面面积的有限部分。所有三种方法都提供总（毛细管+薄膜）界面面积的测量，主要区别在于薄膜相关面积是显微断层扫描方法的光滑表面等效物。显微断层扫描方法的优点是能够明确确定总界面面积和毛细管相关界面面积，这对于示踪剂测试方法来说是有问题的。
Air-water interfacial areas as a function of water saturation were measured for a sandy, natural porous medium using two methods, aqueous-phase interfacial partitioning tracer tests and synchrotron X-ray microtomography. In addition, interfacial areas measured in a prior study with the gas-phase interfacial partitioning tracer-test method for the same porous medium were included for comparison. For all three methods, total air-water interfacial areas increased with decreasing water saturation. The interfacial areas measured with the tracer-test methods were generally larger than those obtained from microtomography, and the disparity increased as water saturation decreased. The interfacial areas measured by microtomography extrapolated to a value (147 cm(-1)) very similar to the specific solid surface area (151 cm(-1)) calculated using the smooth-sphere assumption, indicating that the method does not characterize the area associated with microscopic surface heterogeneity (surface roughness, microporosity). This is consistent with the method resolution of approximately 12 mu m. In contrast, the interfacial areas measured with the gas-phase tracer tests approached the N-2/BET measured specific solid surface area (56 000 cm(-1)), indicating that this method does characterize the interfacial area associated with microscopic surface heterogeneity. The largest interfacial area measured with the aqueous-phase tracer tests was 224 cm(-1), while the extrapolated maximum interfacial area was approximately 1100 cm(-1). Both of these values are larger than the smooth-sphere specific solid surface area but much smaller than the N-2/BET specific solid surface area, which suggests that the method measures a limited portion of the interfacial area associated with microscopic surface heterogeneity. All three methods provide measures of total (capillary + film) interfacial area, a primary difference being that the film-associated area is a smooth-surface equivalent for the microtomography method. An advantage of the microtomography method is the ability to determine explicitly both total and capillary-associated interfacial areas, which is problematic for the tracer-test methods.