Phytoremediation as bioavailable contaminant stripping tool: a case study of hg contaminated soil

The Bioavailable Contaminant Stripping (BCS) efficiency was evaluated analyzing the labile-Hg residue in the soil after the plants growing. Combined treatments with a plant hormone (cytokinine) and a thioligand (ammonium thiosulfate, TS) to strengthen Hg uptake by two crop plants (Brassica juncea and Helianthus annuus) were tested. Plant biomass, evapotranspiration, Hg uptake and distribution following treatments were compared. Results indicate the plant hormone, cytokinine (CK) foliar treatment, increased the evapotranspiration rate in both tested plants. The Hg uptake and translocation in both tested plants increased with simultaneous addition of CK and TS. B. juncea was the most effective in Hg uptake; the application of CK to plants grown in TS-treated soil led to an increase in Hg concentration of 232% in shoots and 39% in roots with respect to control. H. annuus gave a better response in plant biomass production and the application of CK to plants grown in TS-treated soil led to an increase in Hg concentration of 248% in shoots and 185% in roots with respect to control plants. Plants grown with CK and TS in one growing cycle significantly affected labile-Hg pools in soil characterized by sequential extraction, but did not significantly reduce the pseudototal metal concentration in the soil.