Measurement of NAPL–water interfacial areas and mass transfer rates in two-dimensional flow cell

The nonaqueous-phase liquid (NAPL)–water interfacial area and the mass transfer rate across the NAPL and water interface are often key factors in in situ groundwater pollution treatment. In this study, the NAPL–water interfacial area and residual NAPL saturation were measured using interfacial and partitioning tracer tests in a two-dimensional flow cell. The results were compared with previous column and field experiment results. In addition, the mass transfer rates at various NAPL–water interfacial areas were investigated. Fe²⁺-activated persulfate was used for in situ chemical oxidation remediation to remove NAPL gradually. The results showed that the reduction of NAPL–water interfacial areas as well as NAPL saturation by chemical oxidation caused a linear decrease in the interphase mass transfer rates (R² = 0.97), revealing the relationship between mass transfer rates and interfacial areas in a two-dimensional system. The NAPL oxidation rates decreased with the reduction of interfacial areas, owing to the control of NAPL mass transfer into the aqueous phase.