期刊
SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
卷 64, 期 1, 页码 54-61出版社
WILEY
DOI: 10.2136/sssaj2000.64154x
关键词
-
类别
Time domain reflectometry (TDR) has been used by soil scientists to determine soil water content (theta), A waveform analysis determines an apparent dielectric number (epsilon(a)) which can often be empirically related to epsilon. Bound water near colloid surfaces has different properties than free water. At the gigahertz frequencies used for TDR, free water has a negative temperature effect but bound water has a positive temperature effect on dielectric number. Long coaxial cables reduce the higher frequencies of the TDR equipment, which can influence the frequency dependent epsilon(a)of bound water. The objective of this study was to determine the effect of coaxial cable length and temperature on apparent dielectric properties for samples with and without large amounts of bound water. Two undisturbed columns of Okoboji mucky silty day loam (fine, smectitic, mesic cumulic Endoaquoll) with a specific surface area of 286 m(2) g(-1) and two packed sand samples with calculated surface areas of 0.01 m(2) g(-1) were used for the experiment. The epsilon(a) was determined at four table length combinations, three temperatures, and a range of theta, The temperature correction factors for Okoboji ranged from 0.008 to 0.012 theta/degrees C, depending on cable length. Long cables increased the rise time 41%, which decreased the frequency bandwidth. The Okobuji samples had a bulk electrical conductivity as high as 0.14 S m(-1), which hampered determination of the anal part of the waveform. In summary for Okoboji, cable length and temperature had a greater effect on epsilon(a) than did theta. Nigh surface area samples should be calibrated using the same cable length used for measurements, and the temperature effect should be incorporated.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据