Abstract:

The interfacial area between dense NonAqueous Phase Liquid (DNAPL) and water in porous media is a key parameter determining the dissolution rate of DNAPL in groundwater. In the present study, the specific DNAPLwater interfacial area (Anw) and DNAPL saturation (Sn) were respectively measured by using interfacial partitioning and bulk partitioning tracer tests in a homogeneous twodimensional flow cell. The relationship between Anw and Sn was also analyzed. C18H29NaO3S (SDBS), Alcohol (2,4Dimethyl3Pentanol), and CaBr2 were used as the interfacial partitioning tracer, bulk partitioning tracer, and nonreactive tracer, respectively. Fe2+activated persulfate was used for insitu chemical oxidation (ISCO) remediation, to change Anw and Sn with increased pore volumes (PV) of persulfate. The results showed that, Anw decreased from 206 cm2 to 37 cm2 by the rate of 14 cm2/PV and Sn decreased from 1.34% to 0.33% by the rate of 0.1%/PV. The observed interfacial area decreased linearly with the decreasing of the NAPL saturation (Anw=146×Sn, R2=0.987), which can be used as a simple method to estimate the interfacial area between NAPL and water in porous media. The analysis of impacts showed that, the breakthrough curves of tracers exhibited shoulder and tailing because of the increase of porosity with the variation rate 20.7%. As a result, the retention time of nonreactive tracers increased 5.6%, while the interfacial area decreased 6.8%.

Key words: flow cell, DNAPL, interfacial partitioning, bulk partitioning, persulfate