Phytoremediation of Pb and Cu contaminated soil with maize and microencapsulated EDTA

Chelate-assisted phytoextraction using agricultural crops has been widely investigated as a remediation technique for soils contaminated with heavy metals with low mobility.Here,we report the use of a controlled-release microencapsulated EDTA(Cap-EDTA) by emulsion solvent evaporation to phytoremediate soil contaminated with Pb and Cu.Incubation experiments were carried out to assess the effect of Cap and non-microencapsulated EDTA(Ncap-EDTA) on the mobility of soil metals.Simultaneously phytoextraction efficiencies of maize after Cap and Ncap-EDTA application were tested in pot experiments.The results showed that EDTA effectively increased the mobility of Pb and Cu in the soil solution and Cap-EDTA treatment provided lower but more constant water-soluble concentrations of Pb and Cu in the soil solution.Maize shoot concentrations of Pb and Cu were lower with Cap-EDTA application than with Ncap-EDTA.However,shoot dry weight was significantly higher with Cap-EDTA application.Consequently,the Pb and Cu phytoextraction potentials of maize significantly increased with Cap-EDTA application compared with the control and Ncap-EDTA application.Addition of Cap-EDTA(3 mmol·kg-1) significantly increased the Pbphytoextractioneffciencyof maize to 1.26 mg pot-1of Pb in one growing season,almost a 1.9-fold increase compared with the control and a 1.4-fold increase compared with corresponding Ncap-EDTA(3 mmol·kg-1) applications.The risk of groundwater contamination may,thus,be alleviated and plant uptake of Pb and Cu may increase after incorporation of Cap-EDTA.It is concluded that Cap-EDTA is a better choice than EDTA for Chelate-assisted phytoextraction.