Measurement of initial soil-water contact angle of water repellent soils
Measurement of initial soil-water contact angle of water repellent soils
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DOI：
10.2136/sssaj1999.03615995006300030002x
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发表时间：
1999-05-01
影响因子：
2.9
通讯作者：
Yates, SR
中科院分区：
文献类型：
--
作者：
Carrillo, MLK;Letey, J;Yates, SR
拒水土壤在世界各地普遍存在。排水性显著影响入渗、蒸发和其他水-土相互作用。水-固接触角(Theta)、水滴穿透时间(WDPT)和90度表面张力(GAMMA(ND))等指标被提出用来表征水的拒水程度。许多土壤的拒水性不是稳定的，而是随着时间的推移而变化的。目前尚无测量初始土-水接触角的方法。本研究的目的是建立一种测量初始土-水接触角的技术。我们结合以前发表的理论关系，建立了方程cos theta=[(Gamma(Nd)/Gamma(W))(1/2)-1]和h(P)=2[(Gamma(W)Gamma(Nd))(1/2)-Gamma(W)]/rRhog，其中Gamma(W)是水表面张力，h(P)是突破压头，Ris是孔隙半径，Rho是水密度，g是重力常数。这些关系的有效性是通过用十八胺或泥炭苔藓的溶剂提取物处理两种沙子材料来创建不同程度的拒水性来建立的。研制了一种测量h(P)的仪器。如方程所示，h(P)与γ(ND)(1/2)之间存在线性关系。根据斜率h(P)-伽马(ND)(1/2)曲线计算rTVas的值，并将该r值与毛细血管上升方程中的h(P)相结合来计算cos theta。在cos theta和伽马(ND)(1/2)之间的测量和预测关系之间有很好的一致性。主要结论是，可以通过测量伽马(ND)来确定theta的值，这在野外或实验室很容易做到。
Water repellent soils rue common throughout the world. Water repellency significantly affects infiltration, evaporation, and other water-soil interactions. Various indices, such as the water-solid contact angle (theta), water drop penetration time (WDPT), and 90 degrees surface tension (gamma(ND)), have been proposed to characterize the degree of water repellency. The water repellency of many soils is not stable, but changes,vith time after contact with water. No method is available to measure the initial soil-water contact angle. The purpose of this study was to establish a technique to measure the initial soil-water contact angle. We combined previously published theoretical relationships to develop the equations cos theta = [(gamma(ND)/gamma(w))(1/2) -1] and h(p) = 2[(gamma(w)gamma(ND))(1/2) - gamma(w)]/r rho g, where gamma(w) is the water surface tension, h(p) is the breakthrough pressure head, ris the pore radius, rho is the water density, and g is the gravitational constant. The validity of these relationships was established by treating two sand materials with octadecylamine or solvent extracts from peat moss to create various levels of water repellency. An instrument was developed to measure h(p). A linear relationship was found between h(p), and gamma(ND)(1/2), as specified by the equation. The value of r tvas computed from the slope h(p) vs. gamma(ND)(1/2) curve, and this r value was combined with h(p) in the capillary rise equation to compute cos theta. Good agreement was found between measured and predicted relationships between cos theta and gamma(ND)(1/2). The major conclusion is that the value of theta can be determined by measuring gamma(ND), which is easily done in the field or laboratory.