Chelator-Enhanced Phytoextraction Coupling with Soil Washing to Remediate Multiple-Metals-Contaminated Soils

Abstract

The phytoremediation of metal-contaminated soils in combination with chemical methods such as soil washing could be more effective than single technology. In this study, pot experiments were carried out to study the effects of chelators including a mixture of chelators (MC), monosodium glutamate waste liquid (MGWL), and ethylene diamine tetraacetic acid (EDTA) to enhance Zn, Cd, and Pb uptake by Sedum alfredii Hance. The metal washing efficiency and the environment risk caused by these chelators were also assessed. Furthermore, the rhizofiltration with Rumex crispus was established to investigate the potential of plant hairy roots to remove metals in leachates. Results showed that compared to MGWL and EDTA, MC significantly improved Cd phytoextraction efficiency and left lower environment risk to underground water. MC may be the appropriate choice to enhance phytoextraction by S. alfredii. Leaching with the MC or EDTA removed Pb, to which phytoextraction is not effective. However, heavy metals and organics in leachates were also increased with the addition of chelators and could lead to the pollution of underground water, particularly with EDTA and MGWL. The combination of MC enhanced phytoextraction with hyperaccumulator S. alfredii and in situ soil washing could be an interesting technology to remediate metals (Zn, Cd, and Pb)-contaminated soils if an appropriate leachate handling method is found.