Aqueous extracts from the selected hyperaccumulators used as soil additives significantly improve accumulation capacity of Solanum nigrum L. for Cd and Pb

The effects of soil treatment with aqueous extracts from three hyperaccumulators on Cd and Pb accumulation by Solarium nigrum L. were determined. The stem (S-RG) and leaf extracts (L-RG) of Rorippaglobosa (Turcz.) Thell., and stem extract (S-BP) of Bidens pilosa L. significantly enhanced Cd and Pb total accumulation capacity of S. nigrum compared to control (by 44 %, 47 %, and 29 % for Cd and by 28 %, 28 % and 21 % for Pb, respectively), while EDTA caused its 9 % and 15 % decrease due to the plant biomass reduction (by 33 %). The leaching experiments reflected affinity of additives to metal mobilization in soils. The concentrations of total organic acid in S-RG, L-RG and S-BP were the highest among studied extracts, which besides the beneficial effect on the soil environment (microbe number and enzyme activities), may be partial reasons of strong promotion of S. nigrum accumulation capacity for Cd and Pb. It was shown that hyperaccumulation properties of a plant are not a prerequisite of enhancing effect of the plant-based soil additive on the metal accumulation capacity of the target living hyperaccumultor. The plant-based chelators were found to be promising candidates for EDTA and other chemicals replacement in promoting efficient and environmentally safe phytoremediation.