Effects of different application methods of mixed chelators on remediation of heavy metal contaminated soil in interplanting system

Objective To develop a plant-chemical remediation technique in soil contaminated by heavy metals with application prospects.

Method Mixed chelators (MC) were applied to Sedum alfredii and Zea mays interplanting system with different application methods in pot experiments. As a fortification agent for phytoextraction and a washing agent for heavy metals, the effects of MC on soil remediation were studied.

Result The efficiency of heavy metal extraction by plants was improved and soil heavy metals could be partly leached by MC in S. alfredii and Z. mays interplanting system. Heavy metal amounts washed by MC twice were more than that of a single washing. Through interplanting and chemical washing, total Cd, Zn and Pb in soil decreased by 30.7%-33.0%, 11.9%-14.7% and 13.3%-16.4% respectively. The number of soil rhizospheric microorganism was different from that of a single crop in the S. alfredii and Z. mays interplanting system. MC application increased the number of bacteria and actinomycetes in the interplanting system, while high dosage MC washing reduced the number of soil microorganisms.

Conclusion The removal of heavy metals by combining interplanting with chemical washing technology is more efficient than by phytoextraction. Zn and Cd removal can be achieved by phytoextraction while Pb removal mainly relies on MC washing. The interplanting and washing technique can accelerate remediation of Cd, Zn and Pb in combination pollution soils.