Numerical and Analytical Simulation of Transport of Cd, Ni, and Zn in Disturbed and Undisturbed Saturated Loamy Soil Columns

Contamination of soil, water, and air with heavy metals is an environmental issue and of particular importance due to its toxicity, persistence, and mobility in soil. For a better understanding of the environmental behavior and risks associated with heavy metals, modeling their fate and transport is prioritized as an efficient tool. In the present research, the transport of the heavy metals cadmium (Cd), nickel (Ni), and zinc (Zn) in two disturbed and undisturbed loamy soils with the initial concentrations of 50, 100, and 150 mg/L was simulated using CXTFIT and Hydrus-1D as analytical and numerical models, respectively. The results showed that both the models can simulate the transport of heavy metals and describe the BreakThrough Curves (BTCs) with a coefficient of determination (r2) of higher than 0.9 and a root mean square error (RMSE) of less than 0.06. However, the analytical CXTFIT model showed a better fit to the BTCs compared to the numerical Hydrus model. Also, the models showed better efficiency in the disturbed soil than undisturbed soil. With the increase in the concentration of all the three heavy metals, the retardation factor (R) decreased and indicated a trend as Zn Ni Cd. The hydrodynamic dispersion coefficient (D) in the undisturbed soil was estimated to be higher than in the disturbed soil and followed the trend of Cd≥Zn≥Ni. The evaluation of the results showed that despite the better performance of the CXTFIT model, there is no major difference between the two models.