Measurement of Oil and Water Contents In Oil-Contaminated Soil with a Thermo-Time Domain Reflectometry Probe.

Oil spills from underground storage tanks and/or pipelines may result in serious environmental contamination. Oil spills are usually detected after contamination of surface- or ground-water has already proceeded. If oil spills are detected in the early stage, the serious contamination would be prevented or be minimal. We developed a procedure to measure water and oil contents in unsaturated soil. The thermal and dielectric properties of soil mixed with oil, water, and air were measured in the laboratory to estimate oil and water contents in soil using a thermo-time domain reflectometry (TDR) probe. Sandy and loamy soils were mixed with various known amounts of water and kerosene or vegetable oil in a 100 cm3 metal container. Soil heat capacity was measured with a dual-probe heat-pulse (DPHP), and was soil dielectric constant with TDR. Heat capacity linearly increased with increases in water and/or oil contents. Dielectric constant measured was expressed using a modified-dielectric mixing model. We had two equations expressing heat capacity and dielectric constant of oil-contaminated soil with two unknowns, i.e. water and oil contents. The two equations were analytically solved with the information on bulk heat capacity and bulk dielectric constant measured with a thermo-TDR probe to estimate oil and water contents in the soil.