Abstract
Partitioning Interwell Tracer Test （PITT） is a useful tool for quantifying the volume of Non-Aqueous Phase Liquids （NAPL） present in aquifer. The volume is estimated by the retardation factor of a partitioning tracer relative to the transport of the non-partitioning tracer that was determined from the trac-er breakthrough curves （BTCs） However, the equi-librium partitioning would not be completed during every PITT in the actual fi eld, where high saturation NAPL areas such as free‒phase pools and macro‒scale entrapment zones are existed. In this study, we made five laboratory experiments focused on the diameters of NAPL entrapped porous material. Experiments re-vealed that, the accuracy of estimated NAPL volume by PITT was not aff ected by the diameter. In contrast, the tailings of the BTCs were affected by the diameter. Tracer diffusion distance would be longer in the NAPL entrapped porous material that has a large diameter, and therefore, the tailing of the BTCs might become more prominent.
