Subsurface contamination by non-aqueous phase liquid (NAPL) has become a serious environmental issue. Therefore, it is necessary to estimate the NAPL content (θNAPL) in unsaturated soil to detect and monitor the NAPL contaminations in soil and groundwater. The objective of this study was to investigate the relationship between θNAPL and permittivity (K) in unsaturated sandy soil as a fundamental study to estimate the θNAPL. An ADR (Amplitude Domain Reflectometry) method was used to measure the K in the soil including the NAPL which was a castor oil as light NAPL or a HFE-7100 as dense NAPL. The experimental study indicated the linear relation between θNAPL and K in unsaturated soil with soil-NAPL-air. Using this relationship, we can estimate the θNAPL. On the other hand, although we obtained the relationship between θNAPL, θw and (root) K in unsaturated soil with soil-NAPL-water-air, it was not possible to estimate the θNAPL using this relationship.
Amplitude Domain Reflectmetry
Soil and groundwater contamination