Multi-dose applying EDTA to decrease the potential groundwater contamination using rainbow pink (Dianthus chinensis) for enhanced phytoextraction

Synthetic chelating agents are used to increase the phytoextraction of metals from contaminated soils, however the increased bioavailability of the metals may increases the potential risk of groundwater contamination. In this study, 4 mmol EDTA kg−1 was applied using four application methods to a Cd-, Zn-, and Pb-contaminated soil to evaluate the effects of multi-dose EDTA application on the metals concentrations in the soil solution, soil (as extracted by different methods), and shoots of rainbow pink (Dianthus chinensis). Results showed that application of 4 mmol kg−1 one time or application of 2 mmol kg−1 two times, significantly decreased the concentration of Cd, Zn, and Pb in the soil solution at the end of experiment (42nd day) compared with the application of 0.67 mmol kg−1 six times during 6 weeks experiments. Application of 2 mmol kg−1 two times significantly decreased the deionized water-extractable Cd and Pb concentrations in the soil compared with the application of 0.67 mmol kg−1 six times. However, there were no any effects of the different application methods on the concentration and total removal of Cd, Zn, and Pb in the shoots of rainbow pink. Results revealed that application of 2 mmol kg−1 two times was effective to decrease the potential groundwater contamination.