Since permeability of field soils is strongly affected by dry bulk density, knowledge of spatial distribution of dry bulk density is beneficial to predict water and chemical transport through soils. In this study, field soil dry bulk density was estimated by using Amplitude Domain Reflectometry (ADR) data. The experiment was sited at the Sakae-cho experimental field of Tokyo University of Agriculture and Technology (TUAT) covered by Andisol soil. The field of 4 X4m in large was divided into 81 small plots of 0.5X0.5m each. The ADR probe was operated in every small plot, and the ADR output voltage was measured by using digital voltmeter. Soil samples were taken by using the steel ring of 100 cm3 in volume. The results showed that the estimated dry bulk density agreed well with the measured dry bulk density. The regression coefficient (R2) ranged from 0.4 to 0.7. Dry bulk density estimated by using the ADR data and wet bulk density (R2=0.5-0.7) had greater accuracy than that by using the ADR data and mass wetness (R2=0.4-0.6). Furthermore, spatial variability, which was expressed by semivariogram, of the measured and the estimated dry bulk density by using the ADR data and wet bulk density agreed well. However, spatial variability of the dry bulk density estimated by using the ADR data and mass wetness showed different trend to others. This indicated that the estimated dry bulk density with wet bulk density had better performance to predict dry bulk density than that with mass wetness.
Partitioning Interwell Tracer Test (PITT) developed in the petroleum industry is a useful method to quantify the volume of Non-aqueous phase liquid (NAPL) in contaminated aquifer. PITT provides us information about the characterization of the NAPL volume and distribution in relatively large scale area. When we perform PITT, we use the basic assumption that tracers are partitioned to NAPL completely during PITT. However, the assumption is not verified yet. Under practical conditions, we have to be careful of (1)loss of NAPL during PITT, (2) NAPL migration process, (3) sorption of NAPL to organic materials or minerals in aquifer, (4) in-homogeneous tracer partitioning to NAPL because of the heterogeneous NAPL distribution and form, (5) accuracy of measuring tracer partitioning coefficients. The purposes of the study are (1) to estimate the unknown quantity of NAPL placed in a column filled with glass beads and water, and in a pipette filled with water, and (2) to analyze the accuracies of these estimations by PITT method. As a result, the ratios of estimated NAPL volumes and actual NAPL volumes ranged from 0.59〜1.4. The reliability of NAPL estimation by means of PITT decreased when the flow rates of tracers were too low.
This study evaluated the performance of a rainwater utilization system. Excess rainwater is drained from rooftops into an underground container from which the water infiltrates from the base and sides into the surrounding soil of a vadose zone. The saturated hydraulic conductivity of the soil where this system was used was very low at the surface and higher in the deeper layer where the container was located. A simple method was proposed to estimate the steady recharge rate of excess rainwater from the buried container into the surrounding soil of the vadose zone. By modifying the steady recharge equation, which is widely used in the theory of the Guelph Permeameter, a steady recharge rate from the container was calculated from the measured value of saturated hydraulic conductivity and the size of the container.