Irrigation of Helianthus annuus with Pb-polluted water: improvement of phytoremediation using vermicompost

For investigating the effect of vermicompost (VC) on improving phytoremediation of Pb by sunflower (Helianthus annuus) cultivar Lakumka, a factorial experiment was conducted in the pots containing soil or its mixture with 10% VC, in a greenhouse with controlled condition at 2018. After 3 weeks irrigation with normal water, plants were daily irrigated with high Pb-polluted water (0, 1000, 1500 or 2000 mg L-1) up to 3 more weeks. Then, changes in plant biomass, Pb accumulation in root and shoot, and absorption of some mineral nutrients were measured. Results showed that the shoot biomass of sunflower was not affected by Pb treatments. Pb accumulation in root was increased in a dose dependent manner, where in plants under 2000 mg L-1 it reached to 31 times more than that of control. This increase was reinforced by VC so that in Pb+VC-treated plants the bioconcentration factor (BCF) of Pb in roots was higher than those not-amended with VC. However, both plant groups had a good BCF much more than 1.  Pb accumulation in leaves of Pb-treated plants showed a significant increase, where VC caused a significant decrease in its accumulation. Effect of VC and Pb treatments on calcium, magnesium and zinc concentration of root and leaf did not follow the regular changes. Overall, sunflower cultivar Lakumka was an appropriate accumulator of Pb. VC can improve Pb phytoremediation by sunflower.