Mobility of lead, zinc and cadmium in alluvial soils heavily polluted by smelting industry

In order to determine the mobility of Pb, Zn and Cd in soils from the Pribram region (Czech Republic) heavily contaminated by metallurgy, two profiles of alluvial soils were closely studied. Total contents of heavy metals were determined after digestion with a mixture of HF and HClO4. Heavy metal mobility was assessed using the mobility factor (MF) that represents the proportion of heavy metals present in the exchangeable and carbonate bound fraction based on the Tessier's sequential extraction procedure. The MF ranged from 2 to 46% for lead, 19 to 62% for zinc and 61 to 94% for cadmium. The profile distribution of zinc and cadmium showed a variable development with depth, which is caused by high amounts of these metals present in labile forms. The profile distribution of lead (the least mobile metal) is characterized by a gradual decrease with depth. The results indicate a higher contamination of the soil profile situated 2.5 km away from the smelter in comparison with the profile in its close vicinity. This fact confirms the existence of extreme fluvial contamination.