Influence of zeolite, apatite and Fe-oxide on Cd and Pb uptake by crops.

Natural zeolite (clinoptilolite), hydroxyapatite and an iron-oxide waste by-product (Fe-rich, a trademark name of E.I. du Pont de Nemours) were added to an artificially contaminated Appling soil to immobilize and limit the uptake of metals by crops. A greenhouse pot study employed spiking the soil with Cd and Pb from metal flue dust. Maize (Zea mays) and barley (Hordeum vulgare) were planted in 7-kg potted soil to determine the effects of Cd and Pb on plant growth and uptake. Sequential extraction of soil indicates the substantial influence of soil pH and type of ameliorant on the chemical form and bioavailability of the metals. Data indicates that a dose of 50 g/kg of soil of iron-oxide appears to be very effective, based on the yields, metal contents of plant tissues and available forms of Cd and Pb in the soil. Lower doses of zeolite and apatite (15 g/kg and 4 g/kg soil, respectively) in most cases also reduced significantly the uptake of Cd and Pb by crops.