Synchronized adsorption studies with Pb, Cu, Zn and Cd were attempted for coffee growing soils of south India with graded doses of the metals. Among the four soils from different agro-climatic regions the affinity sequence was in the order Pb > Cu > Zn > Cd except in one where preferential adsorption of Cu exceeded that of Pb. Among the metals Pb and Cu were strongly immobilized, while Zn and Cd were least adsorbed. The incumbent toxicity of Pb and Cu were effectively nullified, whereas free Zn and Cd in the vadose zone pose the problems concerned to nutrition and pollution, respectively upon leaching and runoff losses.
Synchronized adsorption, affinity sequence, heavy metals
