The effect of Langmuir sorption on pump-and-treat remediation of a stratified aquifer

Abstract An analytical solution is derived for the mass flux during remediation of a perfectly stratified aquifer by pumping. The idealized plume and the flow field are defined in a circular-cylinder geometry, where the aquifer is assumed to display spatial variability in the hydraulic conductivity, K , in the vertical direction only. The interaction between the solute in the mobile and immobile phases is described by the nonlinear Langmuir equation, which for a remediation case introduces additional dispersion to that caused by the heterogeneous flow conditions. Calculations for the case of variable K and constant sorption parameters show that the parameters expressing heterogeneity ( σ Y 2 ) and sorption capacity ( N 0 ) may cause changes of one order of magnitude, or more, in the time periods needed to fulfill the goals of remediation operations. For a given concentration, increased values of σ Y 2 and/or N 0 lead to prolonged cleanup times. Furthermore, the effects of different cleanup goals, expressed as the mass fraction needed to be recovered, and the concentration-dependent effect, i.e. the variation in cleanup time with concentration for given natural conditions, are found to be important. Simultaneous spatial variability in K and N 0 is modeled assuming different degrees of negative correlation between these parameters. Calculation results based on very limited field data that spatial variability in N 0 may have relatively small impact on cleanup times. The degree of negative correlation is found to be an important factor for determining whether spatial variability in N 0 needs to be included in the analysis.