Abstract
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.
Highlights
The nonaqueous-phase liquid (NAPL)–water interfacial area is a key parameter for the remediation of organic contaminant source zones and risk assessment (Cho et al ; Carroll et al )
1.31 1.23 1.34 4 θw is the water content; ρb is the bulk density; Rift is the retardation factor of interfacial partitioning tracer; Rpt is the retardation factor of bulk partitioning tracer; Anw is the specific NAPL–water interfacial area; Sn is the mean immiscible liquid saturation for the tracer sweep area; CV is the coefficient of variation
The results showed that compared with the values from one-dimensional column study, the measured maximum specific interfacial area value in the flow cell was closer to the values obtained from previous field experiments employing the tracer test method
Summary
The nonaqueous-phase liquid (NAPL)–water interfacial area is a key parameter for the remediation of organic contaminant source zones and risk assessment (Cho et al ; Carroll et al ). Two primary methods are available to measure NAPL–water interfacial areas for natural porous media systems, interfacial partitioning tracer tests (IPTTs) (Brusseau et al ) and synchrotron X-ray microtomography (Brusseau et al b, ). The IPTT method provides indirect measurements of interfacial area based on the retention behavior of tracers that accumulate at the interface. Previous studies have employed the IPTT to determine NAPL–water interfacial areas in column-scale laboratory experiments (Dobson et al ; Narter & Brusseau ). Multiple-dimensional flow cell experiments, with conditions closer to those in the field, are seldom carried out. It is of particular significance to compare the measurement of NAPL–water interfacial areas in different dimensions
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