The influences of ionic strength and permeability on DNAPLs representative elementary volume in porous media

Abstract Dense nonaqueous phase liquids (DNAPLs) have led to widely distributed groundwater contamination due to their widespread applications and accidental spills. To investigate influences of two factor-ionic strength and permeability on the representative elementary volume (REV) of DNAPL, four experiments are conducted in two-dimensional (2D) porous media to investigate perchloroethylene (PCE) migration and associated REVs. The permeability and ionic strength of four experiments are set as different schemes. PCE migration and REVs are estimated by moment analysis and the criteria of the relative gradient error ( e g i ). Results suggest that the permeability and ionic strength are of significant effects on REVs of PCE. Higher permeability of porous media can promote the vertical infiltrate rate of PCE in aquifer. Simultaneously, higher ionic strength can lower the second moments of PCE plume and increase the GTP of PCE mass. More importantly, higher permeability has increased the REV of PCE saturation ( S o ) with absolute errors of 1.35 mm and 2.71 mm under conditions of low and high ionic strength. Besides, higher permeability has decreased the REV of PCE-water interfacial area ( A OW ) with absolute errors of 2.76 mm and 1.09 mm under conditions of low and high ionic strength. What’s more, ionic strength has no apparent effects on S o -REV sizes when permeability is high (absolute error equals to 0.16 mm between low and high ionic strength). However, high ionic strength can decrease the minimum REV sizes of S o when permeability is low (absolute error is 1.52 mm). Moreover, high ionic strength can increase minimum REV sizes of A OW with absolute errors of 1.49 mm and 1.01 mm under conditions of high and low permeability. These findings can improve the understanding of DNAPLs behaviors in subsurface environment under complex condition.