EVALUATION OF SORPTION MODELS IN THE SIMULATION OF NAPHTHALENE TRANSPORT THROUGH SATURATED SOILS

To show the effect of sorption model selection, the one-dimensional transport of naphthalene in two saturated porous media was simulated using numerical models, which included the processes of dispersion, advection, and sorption. Three different models describing the sorption process: (1) a local equilibrium model, (2) a first-order kinetic sorption model, and (3) a two-site model (a combination of equilibrium and kinetic sorption model), were examined. In addition, this study considered two types of boundary conditions: constant concentration and constant flux boundary conditions. Simulations were made for data of naphthalene transport through a laboratory soil column packed with Lincoln or Eustis soil series. Numerical simulation results show that the selection of the sorption model had significant effects on the numerical solutions. The numerical solution obtained using either the local equilibrium model or the first-order kinetic sorption model described the experimental data very well from the Lincoln soil column. In contrast, the numerical solution obtained using the two-site model described the experimental data for the Eustis soil better than either the equilibrium or kinetic models. Different boundary conditions had little influence on the numerical solutions. Different amounts of organic carbon in the Eustis (0.66%) and Lincoln (0.036%) soils are thought to cause the differences in breakthrough curves and the response to the sorption processes.