Experimental investigations on spreading and displacement of fluid plumes around an injection well in a contaminated aquifer

Abstract

ｄe concentration of the injected fluid decays smoothly around the location of the corresponding sharp interface, which is beyond the theoretical range. This concentration spread should be considered in redefining outer mixing boundaries around injection well between the injected and ambient contaminated solutions. In this study, a radial transport experiment was performed (naphthol green B was first injected as a contaminant plume followed by potassium permanganate as the remediation agent) to mimic the interface mixing in more realistic conditions. The radial advection–dispersion model (e.g., dominated by interfacial driving, R (C/C0 = 0.5), combined with dispersion mixing) was used to obtain the position of the “boundary”, rf, at the mixing fringe of the injected fluid. The results show that the injected oxidant front ran after the contaminated plume at a migration velocity of more than 1.29 times, increasing the mechanical dispersion difference between potassium permanganate and naphthol green B. The increase in the injection rate and ambient groundwater flow velocity improved the mixing of oxidant and contaminated plume (the area difference between the contaminated plume and the oxidant decreased) but also accelerated the contaminated plume coverage. Changing the injection mode (such as linear injection) was an effective method, which enhanced the mixing of the oxidant-contamination plume and weakly expanded the contaminated plume (The swept area, 254 cm2, was the smallest among the three injection modes). The relationship between injection and mixing needs to be further strengthened.