EVALUATION OF METAL MOBILITY, PLANT AVAILABILITY AND IMMOBILIZATION BY CHEMICAL-AGENTS IN A LIMED-SILTY SOIL

Metal-contaminated soils in the vicinity of industrial sites become of ever-increasing concern. Diagnostic criteria and ecological technolog ies for soil remediation should be calibrated for various soil conditi ons; actually, our knowledge of calcareous soil is poor. Silty soils n ear smelters at Evin (Pas de Calais, France) have been contaminated by non-ferrous metal fallout and regularly limed using foams. Therefore, the mobility, bioavailability, and potential phy,totoxicily of ed, Pb and Zn, were investigated using single soil extractions (i.e. Mater, 0.1 N Ca(NO3)(2), and EDTA pH 7), and vegetation experiments, in paral lel with a biological test based on (iso)enzymes in leaves and roots, before and following soil treatment with chemical agents, i.e. Thomas basic slags (TBS), hydrous manganese oxide (HMO), steel shots (ST) and beringite. No visible toxicity symptoms developed on the above-ground parts of ryegrass, tobacco and bean plants grown in potted soil under controlled environmental conditions. Cd, Zn and Pb uptake resulted in high concentrations in the above-ground plant parts, but the enzyme c apacities in leaves and roots, and the peroxidase pattern indicated th at these metal concentrations were not phytotoxic for beans as test pl ants. The addition of chemical agents to the soil did not increase bio mass production, but treatment with either HMO, ST or beringite marked ly, decreased the mobility of Cd, Zn and Pb. These agents were proven to be effective in mitigating the Cd uptake by plants. HMO and ST decr eased either Pb or Zn uptake by ryegrass. TBS was effective in lowerin g Pb uptake by the same species. Beringite decreased Cd uptake by bean s. If fallout could be restricted, the metal content of food crops in this area should be lowered by soil treatment. However, the difference s in Cd uptake between plant species were not suppressed, regardless o f the type of agents applied to the soil.