Plant uptake and leaching potential upon application of amendments in soils spiked with heavy metals (Cd and Pb)

The aim of this study was to assess the effects of soil amendments (organic and inorganic) on phytoavailability and leaching of cadmium (Cd) and lead (Pb) during enhanced phytoextraction. The vertical column study was carried out to investigate the metal leaching meanwhile studying plant biomass and metals uptake for phytoextraction by Pelargonium hortroum. For this purpose, soil amendments at several concentration levels, such as ethylene diaminetetraacetic acid (EDTA 0, 4, 5 mmol kg^-1), ammonium nitrate (0, 8, 10 mmol kg^-1), citric acid (0, 8, 10 mmol kg^-1), compost (0, 8%, 10%) and titanium dioxide nanoparticles (TNPs, 0, 80, 100 mg kg^-1) were used. Results revealed that EDTA efficiently improved Cd and Pb accumulation (mg kg^-1) in shoots and roots. Cd accumulation was significantly increased by 270%, 44%, 145%, and 6.4% in shoot and 94%, 19%, 48% and 14% in root upon EDTA, ammonium nitrate, citric acid and TNPs application, respectively compared to the control without amendment (WA). Similarly, Pb accumulation was significantly increased by 71%, 58% and 52% in shoot and 88.8%, 70.6% and 64.6% in root upon exposure to higher levels of EDTA, citric acid and ammonium nitrate, respectively when compared to the WA control. Application of TNPs reduced the Pb-accumulation in shoots and roots by 33% and 28%, respectively. Similarly, the Pb-accumulation in shoots and roots was decreased by 39% and 35%, respectively upon compost addition. Plant biomass was significantly increased upon application of soil amendments, with the exception of EDTA. The maximum Cd and Pb uptake was found in citric acid amended soil. Leachate analysis revealed that the concentrations of Cd and Pb were increased by 109% and 101% in leachates upon EDTA application as compared to other amendments. In comparison with other amendments, citric acid may be recommended as an environmentally friendly alternative for non-biodegradable EDTA for enhanced phytoextraction of Cd and Pb.