Effect of Nonlinear Adsorption on Contaminant Transport in Aquifer

Abstract

Contaminant transport phenomena in an aquifer are mainly affected by the advection of groundwater, diffusion and adsorption to the soils. The adsorptive effect has usually been expressed as the retardation factor in numerical mass transport models. The retardation coefficient was treated constant in previous many studies on the assumption that adsorption equilibrium was linear. However, nonlinear adsorption equilibrium has also been reported in soil-contaminant interactions. The adsorption depends on the concentration of contaminant in the nonlinear equilibrium, so that the retardation coefficient needs to adopt the concentration dependency in the case of relatively large adsorptive effects.
This paper expresses the difference of retardation factor using nonlinear adsorption and linear one for the contaminant transport phenomena in the aquifer using a one-dimensional advection-diffusion model. The numerical analysis was conducted under the assumption of the square-pulse response measurement at the output in a column experiment.
The analysis showed the rejoins of the model parameters that nonlinear adsorption was unable to approximate the linear adsorption equilibrium. We need to evaluate the contaminant transport phenomena using nonlinear in that region.