Enhanced phytoremediation of lead by soil applied organic and inorganic amendments: Pb phytoavailability, accumulation and metal recovery.

Chelation of lead (Pb) is an important factor in enhancing the Pb mobility thereby improving availability to promote phytoremediation of Pb from contaminated soil. The study was conducted to evaluate the effect of amendments in enhancing the phytoremediation of Pb in soil. For this purpose, soil was spiked to obtain desired Pb concentrations (0-1500 mg kg-1) and pots were filled. One month old and uniform seedlings of Pelargonium hortoum were transplanted into each pot. Five different amendments i.e. compost (0-10%), ammonium nitrate (0-10 mmol kg-1), TiO2NPs (0-100 mg kg-1), citric acid (0-10 mmol kg-1) and EDTA (0-5 mmol kg-1), were applied. Overall, ammonium nitrate, EDTA and citric acid application increased the Pb concentration, however, compost and TiO2NPs decreased the concentration in roots and shoots. At 1500 mg Pb kg-1, Pb concentration in shoots was increased by 0.9-, 0.6- & 0.8-folds and in roots by 1.8-, 1.3- & 1.7-folds upon EDTA, ammonium nitrate and citric acid application, respectively. TiO2NPs and compost application decreased Pb concentration by 29% & 35% in shoots and 25% & 51% in roots, respectively. At the highest level of Pb (1500 mg kg-1), plant biomass was increased by 26.6%, 19.5%, 17.9% and 18.4% upon application of compost, TiO2 NPs, ammonium nitrate and citric acid, respectively. However, EDTA reduced the plant dry biomass by 28.4%. The accumulated Pb content was recovered as Pb-nanoparticles, which were in anatase phase, size ranged between 98 and 276 nm. Among all the studied amendments, citric acid efficiently increased Pb phytoaccumulation without any toxicity.