Abstract
The concern of soils contaminated with heavy metals coming from commercial fertilizers and / or irrigation with wastewater is even greater when grown with food plants. Several procedures have been proposed to reduce the concentration of heavy metals in the soil; among them, the application of materials such as bentonite, able to absorb these elements, making them less available to plants. The objective of this study was to evaluate the ability of bentonite to the remediation of artificially zinc (Zn) contaminated soils, having the radish as test plant. The experiment was conducted in a greenhouse in a completely randomized design, with four replicates. After the NPK fertilization, 250 mg kg-1 of Zn and bentonite (doses: 0; 30; 60 and 90 t ha-1) application the loamy sand soil was conditioned in 5 kg plastic containers, irrigated to field capacity and incubated during 20 days. At the end of the incubation process the crops were seeded; after 30 days of experiment, the plants were collected separating the aerial and root part, dried, triturated and weighed for plant analyses. The cumulative amount of Zn in dry biomass of the aerial part (shoot) and roots, the translocation index, the translocation factor, the bioaccumulation factor in the plant (BFP) and in the root (BFR), were evaluated. The results were analyzed by the F test and regressions. The dry phytomass of the aerial part increased and the values of BFP and BFR of radish decreased significantly as a function of increasing doses of bentonite, indicating an increase in the adsorption of zinc in the soil, decreasing the concentration in the plant parts. However, the BFP and BFR values were higher than unity, indicating high bioaccumulation potential of radish for this metal. Based on the results, the application of bentonite to the contaminated soils favored their remediation.
