Development of a real time measurement system for tracing water and solute movement in an unsaturated soil column

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An impedance measurement system controlled by personal computer was developed for a real time measurement of water content and the concentration of electrolyte in a soil. column. The efficiency of this system is studied under a constant temperature condition. Contact-type electrodes and non-contact-type electrodes were used and the following conclusions were obtained.Conclusions obtained by using contact-type electrodes were : suseptance of soil had a linear relationship with water content; conductance of soil had linear relationships with electric conductivity of soil water and water content respectively; the theoretical evaluation function was shown and its efficiency was proved to be right by some experiments; the value of suseptance divided by an angular frequency was determined by water content with no relation to the size of soil particles.Conclusions obtained by using non-contact-type electrodes arranged on an outer surface of a soil column were : typical dielectric dispersion phenomenon was measured at frequencies between 100kHz and 1MHz;the measurement system of this study using impedance meters were not good enough for the measurement over the frequencies of several MHz due to some floating components; dielectric constants showed an increasing tendency with relation to the increase of water content; increasing rate of dielectric constants decreased when the concentration of electrolyte of soil water increased; an evaluation function for estimating water content and the concentration of electrolyte of soil water was developed using dielectric constants and electric conductance and it showed its efficiency for tracing unsaturated movement of NaCl solution through a soil column.Consequently, the efficiency of the real time measurement system using impedance meters for measuring the unsaturated movement of solution through a soil column was shown.