Behaviour of lead in a clayey soil treated with contaminated sewage sludge and its absorption by plants

Abstract

In a clayey soil placed in PVC tubes (80cm high and 10cm in diameter) five treatments were applied with sewage sludge contaminated with Pb. Three with lead, in µg.g^-1, at the concentrations of 0 (control); 2,500; 5,000, and two treatments with a mixture of lead + cadmium (as interferer), in µg.g^-1 each, at the concentrations of 2,500 + 2,500 and 5,000 + 5,000 respectively. The soils in the tubes that received the treatment were cultivated with maize during two and a half months in a greenhouse. The soil analyses for the treatments showed heavy metal Pb only at the surface (from 0 to 20 cm depth). In the depth from 20 to 60 cm the concentration was steady showing a non-significant difference between the treatments and control. The Pb concentration interval found in the aerial parts of the plants (13 - 18 µg.g^-1) for all the treatments was inferior to the interval values considered phytotoxic by the literature (30 - 300 µg.g^-1). No interference of cadmium on lead behaviour was observed.