Monday, November 13, 2006
84-6
Undisturbed and continuous measurement of water content, electrical conductivity, and temperature in a soil column equipped with thermo-time domain reflectometry probes.
Hiroyuki Ochiai, "Meiji University, School of Agricul", 1-1-1 Higashimita Tama, 1-1-1 Higashimita Tama, Kawasaki, 214-8571, JAPAN, Kosuke Noborio, Meiji University, Meiji University School Of Agriculture, 1-1-1 Higashimita Tama-ku, Kawasaki-shi Kanagawa, 214-8571, JAPAN, and Masaru Mizoguchi, Univ. of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Bunkyo-ku, Tokyo, 113-8657, JAPAN.
It is important to know underground water and solute movements in various disciplines. This study was designed to understand water and solute movements under temperature gradient conditions. In previous studies multiple numbers of columns with the same initial and boundary conditions were used with an assumption that water and solute movements in all soil columns proceed in the exact same manners. Those soil columns were dissected at a certain time to know water and solute movements with time. Since the homogeneity of soil packed may vary from one column to another, water and solute movements may be affected by the heterogeneity of each soil column. We developed a new soil column equipped with a thermo-time domain reflectometry (TDR) probe to continuously and non-destructively measure water content, electrical conductivity, and thermal properties in soil. Moistened sand was packed in each soil column (78mm in dia. and 25mm long). Nine soil columns including five thermo-TDR-probe-equipped columns were connected to make a 225mm-long column. A constant temperature gradient (0.178oC mm-1) was applied using cascade-connected Peltier modules to the both ends of the long column. The Peltier modules ware controlled to keep a constant temperature. Series of experiments with various initial water contents (0.1, 0.2, and 0.3 m3 m-3) and KCl concentrations (0.1, and 0.2 mol L-1) were conducted in a constant temperature incubator (20oC). At the end of each experiment the long column was dissected for measuring water and KCl contents. For each experiment, mass was conserved very well. With the initial water content of 0.3 m3 m-3, water and solute movements were similar to the results previously reported whereas those movements with the initial water content of 0.2 and 0.1 m3 m-3 were not.