A review of new TDR applications for measuring non-aqueous phase liquids (NAPLs) in soils

The time domain reflectometry (TDR) technique is a geophysical method that allows, in time-varying electric field, the determination of dielectric permittivity and electrical conductivity wide class porous materials. Measurements volumetric water content (θw) soils most frequent application TDR Soil Science Hydrology. In last four decades several studies have sought to explore potential applications TDR. Such (except those conducted on θw estimation) mainly focused monitoring soil solute transport. more recent times, innovative approaches also been implemented extend current fields problem non-aqueous phase liquids (NAPLs) variable saturated soils. NAPLs are organic compounds with low solubility characterised by high mobility vadose zone. Due their toxicity, constitute severe geo-environmental problem, thus making detection observation such substances an increasingly important issue. present paper deals these aims provide up-to-date review main NAPL-TDR studies. To date, literature has three fields: (i) NAPL homogeneous, soils, (ii) layered (iii) during decontamination processes. For exhaustive complete overview research this we recall basic principles signal propagation, functioning typical device, mixing models widely used interpret response NAPL-contaminated