Zinc and cadmium mobility in podzol soils

Zinc and Cadmium advection experiments are described which were carried out using columns packed with (a) Podzol Bh (b) Podzol BFe and (c) sand mixed with goethite. Aqueous NaCl and synthetic soil solutions were used as the mobile phases. The column cation and proton exchange capacities (CEC and PEC values) were determined. The CEC values were found to reflect the organic matter (OM) contents of the soils but not to correlate with the observed elution volumes. Differences in the exchange interactions and an overall lack of reaction of Cd and Zn with OM, at the prevailing pH values were deemed to be responsible. The changes in the Zn and Cd elution behaviour observed in the presence of chloride were rationalised in terms of the formation of CdCl+ and CdCl2 species.