Simulation of Cadmium Transport in Soil Using Convection-Dispersion Equation



For preventing groundwater and soil from heavy metal contamination and/or to decrease contamination, and to clean up the former disposal sites from these metals, one must be beforehand able to predict the movement of these pollutants in soils. In this research in order to describe Cadmium [Cd (II)] transport in soils, we incorporated an equilibrium-kinetic two-site model into the convection-dispersion equation for reactive solutes under steady state water flow conditions in uniform soils. Also the irreversible retention of Cd (II) was described as a first-order kinetic process. For an assessment of Cd (II) movement in soils, five samples with different physical and chemical properties were collected and taken to the laboratory. Miscible displacement experiments were conducted with disturbed soil columns. Model parameters were obtained by fitting model to the experimental data resulting from miscible displacement experiments using a nonlinear least squares (best fit) parameter optimization scheme. The model was applicable in predicting Cd (II) BTCs for different soils representing a broad array of soil properties. By putting these parameters into the model, concentration and retention of Cd (II) with time and depth were calculated for different soils.