Distribution coefficients of Cd, Co, Ni, and Zn in soils

Batch adsorption experiments were conducted with a mixture of solutes at low equilibrium concentrations of Cd (0.7-12.6 μg1^?1), Co (18-118μg1^?1, Ni (22-330 μg 1^?1), and Zn (40-1480 μg1^?1) in 38 different soils. Statistical correlations indicated that metal sorption onto the soils was influenced by the presence of clays and hydrous oxides of Fe and Mn. Based on calculated distribution coefficients for these metals, Co will generally exhibit the highest mobility in soils, but the mobility of Zn will increase faster with decreasing pH. Two types of empirical relationships are developed from these data to estimate values for the distribution coefficients.