Phytoextraction has been suggested as a viable alternative to traditional restoration practices for heavy metal-contaminated soils (e.g., soil removal and disposal in land fill areas, or co-processing in cement), in view of the lower costs and lower environmental impact. This study had the objective of evaluating induced phytoextraction (use of chelating agent) of heavy metals in black oat (Avena strigosa Schreber), sunflower (Helianthus annuus L.) and Bahiagrass (Paspalum notatum Flügge) in polluted soils (soils 2, 3, and 4) of a Pb mining and processing area in Adrianópolis (PR), Brazil. The experiment was conducted in a greenhouse, with three replications. The soil Pb and Zn contents were determined using concentrated HNO3/HCl (3:1). After harvest, the dry biomass and heavy metal contents in the root and shoot parts were determined by nitro-perchloric digestion. The following values of heavy metal content were found in the contaminated soils (2, 3 and 4) (mg kg-1): Pb - 2,598.5 to 9,678.2; Cd - 1.9 to 22.2; Cu - 165.5 to 969.2; Ni - 22.6 to 38.4; Cr - 15.2 to 27.8 and Zn - 87.4 to 894.8. Chelate addition did not induce heavy metal uptake by the plants. Plant development in soil 2 was better and sunflower should be preferred for phytoremediation in areas under similar conditions. In the area surrounding the industrial plant (soil 3) and in the areas with high waste disposal (soil 4), phytoextraction was not efficient. In these environments other native plants and/or exotic Pb-resistant plants should be tested (soil 3) as well as the remobilization of soil with residues to industrial landfills.
citric acid; Pb phytoxicity; metal-accumulating plants
