Sorption and Desorption of Zn, Pb and Cd by Soil under Forest

Batch equilibration studies for Zn, Pb and Cd were conducted to determine the sorbing and desorbing properties for these metals on a forest soil (Rendoll). Adsorption of these metals was described by the Freundlich relationship. Essentially, all of the zinc was adsorbed by soil (0.20–0.30 m) at low initial zinc concentrations (0.5 and 1 mg L⁻¹). Freundlich constants (K) were higher for 0–0.05 m and 0.20–0.30 m soil depths than those from other soil depths indicating the dominant role played by high organic matter content of the former and high pHofthe latter soil depth in the adsorption of these metals. Desorption of these metals, by equilibrating solution showed that much lower amouhts could be desorbed from soil at lower depths (0.2–0.3 m) as compared to other soil depths. The findings suggest that lower depth of a forest soil would be very important as compared to other soil depths for binding cationic heavy metals incorporated through acid precipitation or industrial dust.