Effects of pH and soil texture on the adsorption and transport of Cd in soils

To better understand the adsorption and transport of Cd2+ in soils, column experiments were conducted with various soils and inflow solutions with different pH values. Breakthrough curves (BTCs) of the column tests were fitted using both the equilibrium and non-equilibrium models installed in the program of CXTFIT. Results showed that the equilibrium model fitted most of BTCs reasonably well. Values of the retardation factor (R) and the distribution coefficient (k(d)) for Cd2+ adsorption and transport increased with increasing pH values of the inflow solution and of the soil. However, the clay content was not a key factor to affect R and k(d) for Cd2+ adsorption and transport. The average dispersivity values and the variance values of dispersivity increased with increasing clay content of the soils.