Enhancing Phytoextraction of Lead Contaminated Soils by Carrot (Daucus carrota) Using Synthetic and Natural Chelates

Phytoextraction is a remediation technology for contaminated soils with lead (Pb). The application of chelating agents can be resulted in high efficiency in this method. In current study، the effect of synthetic and natural chelates applicationon efficiency of lead phytoextraction from soil by carrot was investigated. The experiment factors were 1) six levels of Pb (0، 100، 200، 300، 500 and 800 mg Pb kg-1 soil، added as Pb(NO3) 2، 2) chelates (EDTA، NTA and oxalic acid، and 3) chelate concentration (0، 2. 5، 5 and 10 mmol kg-1 soil). The results indicated that EDTA effectively increased the Pb content in soil solution. At the highest applied rate (10 mmol EDTA kg-1)، it resulted in 463-fold increase in extractable Pb، compared to the control treatment. Pb content in the shoot and taproot increased with the chelates application rates. The highest Pb content in the shoot (342. 2±13. 9 mg kg-1) and root (310 ±15. 5 mg kg-1) occurred in 10 mmol kg-1 EDTA when Pb level was 800 mg kg-1. Pbphytoextraction potential increased with increasing thechelate and Pb concentration. Maximum Pb extraction from soil (1208±26. 6 g ha-1 yr-1) during growth season occurred in 10 mmol kg-1 EDTA، when soil Pb level was 800 mg kg-1. It may be concluded that carrot can take up high amount of Pb and concentrate it in its roots and shoots. Thus، it can be introduced as a lead accumulator to phytoextractPb from contaminated soils.