Effect of soil properties on sorption of cadmium in selected soil orders

This study was conducted to evaluate the effect of soil chemical and physical properties on Cd sorption by different soils classified as Entisols, Molisols, Aridisols, and Andisols. Sorption isotherms were obtained using batch experiments in which 25 ml of solution containing a total of 0.8, 1.6, 3.2, 6.4, and 12.8 ppm of Cd2+ were added to 0.5 g soil samples. Cadmium sorption was also evaluated at a constant [Cd]T of 12.8 ppm in four pH levels (5, 6, 7, and 8). The results indicate that, in all the soils used, the Cd sorption is best described by the Freundlich sorption isotherm. The maximum soil sorption capacity b (mg g-1) was significantly correlated with inorganic poorly crystalline iron (Feo- Fep), and the total oxalate extractable iron (Feo) at the probability level of (p < 0.05). Distribution coefficient (kd) values of Cd in soils were significantly correlated to silt %, Feo- Fep, Feo at (p < 0.01); and Fed at (p < 0.05). For all investigated soils, the sorbed amounts of Cd increased with increasing pH. A small change in pH can cause a dramatic change in the sorption capacity of the soil, especially at soil pH values below 6.Corresponding author Dr. Saud S. AL-Oud, Department of Soil Water Science College of Agriculture & Vet. Medicine King Saud University, AlQassim Branch P.O. Box 2460, Riyadh 11451, Kingdom of Saudi Arabia. Email: saloud@ksu.edu.s