Calibration of time domain reflectometry technique using undisturbed soil samples from humid tropical soils of volcanic origin

被引:80
作者
Weitz, AM
Grauel, WT
Keller, M
Veldkamp, E
机构
[1] US FOREST SERV, INT INST TROP FORESTRY, RIO PIEDRAS, PR 00928 USA
[2] UNIV NEW HAMPSHIRE, INST STUDY EARTH OCEANS & SPACE, COMPLEX SYST RES CTR, DURHAM, NH 03824 USA
关键词
D O I
10.1029/96WR03956
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
Time domain reflectrometry (TDR) is used to measure the apparent dielectric number (K-a) in soils. We studied two soil types (Humitropept and Hapludand) of low bulk density (about 0.7 Mg m(-3) at 0.05 m to 0.8 Mg m(-3) at 0.3 m depth) and high organic matter content (about 7% at 0.05 m to 4% at 0.3 m depth). Soils are located in a humid tropical environment (average annual soil water content is 0.51 to 0.58 m(3) m(-3)). For calibration, undisturbed soil blocks, with a TDR probe installed in the center, were saturated and then allowed to dry by evaporation. Volumetric water content was calculated from measured K-a values and from gravimetric measurements. Because we used undisturbed soil samples, our calibration accounts for the natural heterogeneity in soils. We tested the suitability of various calibration functions relating K-a to soil water content for our soils. TDR technique underestimated the actual soil water content by 0.05-0.15 m(3) m(-3), when using the widely applied Topp calibration function. A three-phase mixing model with a geometry parameter, alpha = 0.47, fit our data best. We consider mixing models to be a robust approach for calibration of TDR technique on various soils.
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页码:1241 / 1249
页数:9
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