Phytoremediation: An eco-friendly approach for recovery of soils contaminated by heavy metals

Soil pollution by heavy metals is a risk for environment and public health. Phytoremediation could be an alternative to chemical-physical techniques1-3.
Three microorganisms, Trichoderma harzianum, Saccharomyces cerevisiae and Wickerhamomyces anomalus, were exposed in vitro to eight heavy metals (Ni, Cd, Cu, V, Zn, As, Pb, Hg). T. harzianum has showed the best bioaccumulation ability for V, As, Cd, Hg, Pb4. Then, T. harzianum was selected for the subsequent greenhouse test. Arundo donax and mycorrhized Arundo donax with T. harzianum were exposed for seven months at two different doses (L1 and L2) of the eight heavy metals mixture, to assess whether the symbiotic association could improve the bioaccumulation ability of the superior green plant A. donax.
Heavy metals were determined with ICP-MS5. The mean bioaccumulation percentage values of A. donax for L1 and L2 were, respectively: Ni (31%, 26%); Cd (35%, 50%); Cu (30%, 35%); As (19%, 27%); Pb (18%, 14%); (42%, 45%); V (39%, 26%); Zn (23%, 9%). The values of mycorrhized A. donax with T. harzianum for L1 and L2 were, respectively: Ni (27%, 38%); Cd (44%, 42%); Cu (36%, 29%); As (17%, 23%); Pb (37%, 54%); Hg (44%, 60%); V (16%, 20%); Zn (14%, 7%). A. donax showed the highest BAF (bioaccumulation factor) for Cd (0.50) and Hg (0.45) after exposure to L2; mycorrhized A. donax with T. harzianum showed the highest BAF for Hg (0.60), Pb (0.54) and Cd (0.42) after exposure to L2. The values of the TF (translocation factor) of A. donax were not particularly high, but A. donax mycorrhized with T. harzianum showed high TF values for Cd (0.70) and As (0.56) after exposure to L2, and Zn (0.30) after exposure to L1.

Our results suggest a possible use of both A. donax and A. donax mycorrhized with T. harzianum for phytoremediation processes.

Author(s): Antonio Cristaldi

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