Araujo Juliana B, Brusseau Mark L
Department of Soil, Water, and Environmental Science, The University of Arizona, Shantz Bldg., Tucson, AZ 85721.
Department of Hydrology and Atmospheric Sciences, The University of Arizona, Shantz Bldg., Tucson, AZ 85721.
Water Resour Res. 2020 Jan;20(1). doi: 10.1029/2019WR025470. Epub 2019 Nov 17.
This study investigates the accuracy and reproducibility of air-water interfacial areas measured with high-resolution synchrotron x-ray microtomography (XMT). Columns packed with one of two relatively coarse-grained monodisperse granular media, glass beads or a well-sorted quartz sand, were imaged over several years, encompassing changes in acquisition equipment, improved image quality, and enhancements to image acquisition and processing software. For the glass beads, the specific solid surface area (SSSA-XMT) of 31.6 ±1 cm determined from direct analysis of the segmented solid-phase image data is statistically identical to the independently calculated geometric specific solid surface area (GSSA, 32 ±1 cm) and to the measured SSSA (28 ±3 cm) obtained with the NBET method (NBET). The maximum specific air-water interfacial area (A) is 27.4 (±2) cm, which compares very well to the SSSA-XMT, GSSA, and SSSA-NBET values. For the sand, the SSSA-XMT (111 ±2 cm) and GSSA (113 ±1 cm) are similar. The mean A is 96 ±5 cm, which compares well to both the SSSA and the GSSA values. The XMT-SSSA values deviated from the GSSA values by 7-16% for the first four experiments, but were essentially identical for the later experiments. This indicates that enhancements in image acquisition and processing improved data accuracy. The A values ranged from 74 cm to 101 cm, with a coefficient of variation (COV) of 9%. The maximum capillary interfacial area ranged from 12 cm to 19 cm, for a COV of 10%. The COVs for both decreased to 5-6% for the latter five experiments. These results demonstrate that XMT imaging provides accurate and reproducible measurements of total and capillary interfacial areas.
本研究调查了使用高分辨率同步加速器X射线显微断层扫描（XMT）测量气-水界面面积的准确性和可重复性。填充有两种相对粗粒度单分散颗粒介质之一（玻璃珠或分选良好的石英砂）的柱体，在数年时间内进行了成像，涵盖了采集设备的变化、图像质量的提高以及图像采集和处理软件的改进。对于玻璃珠，通过对分割后的固相图像数据进行直接分析确定的比固体表面积（SSSA-XMT）为31.6±1 cm，与独立计算的几何比固体表面积（GSSA，32±1 cm）以及用NBET方法（NBET）获得的测量SSSA（28±3 cm）在统计学上是相同的。最大比气-水界面面积（A）为27.4（±2）cm，与SSSA-XMT、GSSA和SSSA-NBET值相比非常吻合。对于沙子，SSSA-XMT（111±2 cm）和GSSA（113±1 cm）相似。平均A为96±5 cm，与SSSA和GSSA值相比都很好。在前四个实验中，XMT-SSSA值与GSSA值相差7 - 16%，但在后期实验中基本相同。这表明图像采集和处理的改进提高了数据准确性。A值范围为74 cm至101 cm，变异系数（COV）为9%。最大毛细界面面积范围为12 cm至19 cm，COV为10%。在后面的五个实验中，两者的COV都降至5 - 6%。这些结果表明，XMT成像能够提供准确且可重复的总界面面积和毛细界面面积测量值。
