5:15 PM - 6:30 PM
[AGE27-P05] Quantifying in-situ fine bubble concentration in water and soil with thermo-TDR
Keywords:fine bubble, thermo-TDR, dielectric permittivity, thermal properties
Application of Fine bubbles (FB) for de-contamination of soils has been attracting attentions recently. It is important to understand the behavior of FB in soils, however, effective in-situ measurements of FB concentration in both water and soil have been difficult. In this study, we investigated quantification of FB concentration in water and soil with thermo-TDR.
Two experiments were performed, one was for quantifying FB concentration in water, and the other was to quantify FB concentration in soils. In the first experiment, three differently sized thermo-TDR sensors were placed in a surfactant solution, and FB was produced. Dielectric permittivity of the solution was measured with each sensor. The thermo-TDR sensors were placed either horizontally or vertically to evaluate the effect of probe direction. In the second experiment, two thermo-TDR sensors were inserted into a completely saturated soil column and a quasi-saturated soil column. The FB solution was pumped into the both column, and deictic permittivity, volumetric heat capacity, and thermal conductivity were measured with the thermo-TDR sensors.
It was found that the FB concentration in water could be measured stably from the relative permittivity by using a large size sensor and with the probe placed vertically. The FB concentration in soil was found to be difficult to estimate with thermo-TDR in the case of completely saturated soil because the change in both dielectric constant and thermal properties was small. However, in the case of a quasi-saturated soil, there was a clear change in relative permittivity and thermal property values. It is guessed that the movement of FB was restricted by the enclosed air in the soil, and FB were trapped in the soil column. FB concentration was determined from these changes in dielectric permittivity and thermal properties by using empirical and theoretical equations that express the relative permittivity and thermal properties as a function of water content. Comparing the FB concentrations determined from the relative permittivity and thermal properties, the FB concentration estimated from the thermal properties was relatively large. It is because the thermal properties were affected by the water flow in the soil which was not complete steady-state. In conclusion, thermo-TDR sensor can measure the in-situ FB concentration in water and soil.
Two experiments were performed, one was for quantifying FB concentration in water, and the other was to quantify FB concentration in soils. In the first experiment, three differently sized thermo-TDR sensors were placed in a surfactant solution, and FB was produced. Dielectric permittivity of the solution was measured with each sensor. The thermo-TDR sensors were placed either horizontally or vertically to evaluate the effect of probe direction. In the second experiment, two thermo-TDR sensors were inserted into a completely saturated soil column and a quasi-saturated soil column. The FB solution was pumped into the both column, and deictic permittivity, volumetric heat capacity, and thermal conductivity were measured with the thermo-TDR sensors.
It was found that the FB concentration in water could be measured stably from the relative permittivity by using a large size sensor and with the probe placed vertically. The FB concentration in soil was found to be difficult to estimate with thermo-TDR in the case of completely saturated soil because the change in both dielectric constant and thermal properties was small. However, in the case of a quasi-saturated soil, there was a clear change in relative permittivity and thermal property values. It is guessed that the movement of FB was restricted by the enclosed air in the soil, and FB were trapped in the soil column. FB concentration was determined from these changes in dielectric permittivity and thermal properties by using empirical and theoretical equations that express the relative permittivity and thermal properties as a function of water content. Comparing the FB concentrations determined from the relative permittivity and thermal properties, the FB concentration estimated from the thermal properties was relatively large. It is because the thermal properties were affected by the water flow in the soil which was not complete steady-state. In conclusion, thermo-TDR sensor can measure the in-situ FB concentration in water and soil.