RECLAMATION OF HEAVY-METAL CONTAMINATED SOILS - FIELD STUDIES AND GERMINATION EXPERIMENTS

Field studies and germination experiments have been performed to assess the fertility restoration by different reclamation procedures on heavy metal-polluted soils. In a contaminated area in Switzerland we have investigated the metal accumulation of lettuce (Lactuca sativa L., 'Apollo') on a four different experimental plots: F1 was untouched, F2 was plowed, on F3 the highly contaminated litter was removed, and on F4 the surface layer was removed and replaced with uncontaminated soil The metal content in plant tissue decreased from F1 over F2 and F3 to F4. The lettuce grown on F4 had normal metal tissue concentrations (Cd, 0.92 mg/kg; Cu, 28 mg/kg; Zn, 87 mg/kg) whereas tissue concentrations on the untilled plot F1 were strongly elevated (Cd, 6.1 mg/kg; Cu, 57 mg/kg; Zn, 864 mg/kg). Growth chamber experiments served to test the suitability of different soil substrata for plant development. We have studied the germination and growth of cress (Lepidium sativum L.) and lettuce on different heavy metal-polluted media and observed that the structure of the litter is the main reason for poor development of the seedlings. We conclude that from the reclamation procedures considered, only the replacement of the highly contaminated topsoil will lead to good germination, normal plant development, and heavy metal contents essentially below all toxicity limits.