ABSORBING, IMMOBILIZING OR TRAPPING: FUNCTIONS OF PLANTS IN THE REMEDIATION OF SITES CONTAMINATED BY POTENTIALLY TOXIC ELEMENTS

Abstract

In order to evaluate the potential of different wild plant species in the remediation of sites contaminated by potentially toxic elements (PTEs), plants that were established naturally on mine residues were collected. The concentrations of Zn, Cd, Pb, Cu, Ni and Co in plant tissues were determined, as well as rhizosphere eden mine residues. Based on the factors of bioconcentration and translocation, as well as the limit of phytotoxicity, some species were identified for their potential use as extractors or stabilizers of PTEs. Aster gymnocephalus was classified as an extractor plant of Zn, Cd, Pb and Cu; and Gnaphalium sp., for Cu and Crotalaria pumila for Zn. Pteridium sp. is adequate for phytostabilization of Zn and Cd. To study the function of the plants as a physical barrier that decreases the dispersion of particles that contain PTE, the concentrations of these contaminants in samples from the aerial part of washed and unwashed plants were compared. It was shown that all the species retained on their leaves particles that contain PTEs. In Dichondra argentea and Viguiera dentata the concentration of Zn in unwashed plants was 14 times higher than the concentration on washed plants. The plant coverages composed by various plant species presented at least three different paths of remediation of soils contaminated by PTEs: i) stabilization on the root or the rhizosphere; ii) accumulation in the aerial part; and iii) retention of particles that contain PTEs.