The presence of heavy metals can restrict the use of sewage sludge as a source for plant nutrients since they may contaminate soil, aquifers and plants. Urban sewage sludge from the Treatment Station of Ilha do Governador (ETIG), Rio de Janeiro, Brazil, was enriched with 1.667 mg kg-1 Cd and 8.000 mg kg-1 Zn. After 20 days of incubation under a constant humidity of 50% (g g-1), doses of 0, 20, 40 and 80 t ha-1 were applied to two soil samples (red-yellow Latosol (LV) and red-yellow Argisol (PV)). A greenhouse experiment evaluated the effect of Cd and Zn on the growth of rice (IAC-47) during 126 days in the samples of both soils incubated with the enriched sewage sludge. A complete randomized block design was used with four replications. Plant roots, straw and grains and their respective biomass (dry matter) and Cd and Zn concentrations were evaluated at harvest. The high Cd and Zn doses applied to the soil did not affect plant growth but the plant roots showed high Cd and Zn concentrations as a consequence of the low transference of these elements to the spoots. The Cd and Zn levels found in the whole plant demonstrate a high tolerance of the rice variety IAC-47 to these elements.
heavy metals; soil contamination; Oryza sativa
