SIMULATION OF 1-D SOLUTE TRANSPORT WITH EQUILIBRIUM-CONTROLLED NON-LINEAR SORPTION USING MT3DMS

Groundwater contamination is a rising worldwide issue and it must be treated well as most of the world relies on it. Groundwater pollution occurs when undesirable substances in groundwater rises. Understanding and predicting solute mobility in groundwater simulations helps create pollution treatment. MT3DMS was used to model contaminant movement with non-linear sorption for varied adsorption capacities and intensities. MT3DMS stands for “The modular three-dimensional multispecies Transport model”. It is USEPA-financed development and available opensource. MT3DMS is unique in that it includes three major classes of transport solution techniques (the standard finite-difference method, the particle-tracking-based Eulerian-Lagrangian methods, and the higher-order finite-volume TVD method) in a single code. The combination of these solution techniques is believed to offer the best approach for solving the most wide-ranging transport problems with efficiency and accuracy hence widely used by USGS. In this work, the benchmark problem P2 of MT3DMS package was taken and the chemical reaction package was modified accordingly to our problem and Multiple simulations were run with different adsorption capacities and intensities incorporating nonlinear Freundlich sorption isotherm to analyze BTC trends at a position 8 cm from the source where the pulse input of contamination was discharged for 160 seconds. The simulation lasted 1500 seconds. The observation output files were imported to plot BTCs for trend analysis and visualize simulation results. After comparing the various BTCs, it was found that the adsorption capability of porous medium enhances retention capacity, so contaminants are sorbed and retarded by solid phase more, slowing contaminant movement and delaying BTC peak. For similar adsorption capacity at lower Freundlich exponent, the solid retains more contaminant and the peak is delayed, but as the exponent increases, concentration in aqueous phase increases and peak occurs early as the solid retains less contaminant.