Effect of Sorption Processes on Pump-and-Treat Remediation Practices Under Heterogeneous Conditions

Abstract

We analyze the impact of physical and chemical heterogeneity on solute travel time to a pumping well. Environmental applications related to our work include risk evaluation of a pump-and-treat aquifer remediation practice. We consider a non-conservative solute undergoing reversible linear instantaneous equilibrium sorption. Both the distribution coefficient, K d , and the transmissivity field, T, are considered spatially variable, and are modeled as partially correlated spatial random functions. Groundwater flow and solute transport are then solved within the context of a Monte Carlo framework. Transport of the reactive solute is analyzed within a Lagrangian framework, upon neglecting the influence of local-scale dispersion. From a suite of scenarios, simple expressions of the first two statistical moments of particles travel time to the pumping well are derived as a function of: (i) physical and chemical degree of heterogeneity of the system, and (ii) level of correlation between physical and chemical properties. A key result is that the effects of the chemical and physical heterogeneities on the mean travel time can be decoupled. On the contrary, their relative role in governing travel time variance is more complex, and a separation of the two effects is not observed.