Chelates Induced Phytoremediation Of Heavy Metal Contaminated Soil And The Effect On Form Distribution Of Zn And Soil Enzyme Activity

Heavy metals contaminated soils remediation are the key treatment of contaminated soils. Heavy metals contaminated soil is not only harmful to the soil environment and crops, but also threat to the health of human, so it is essential to carry out remediation of heavy metals contaminated sites. Chelates induced phytoextraction is an effective method for remediation of heavy metals contaminated soil. Adding chelates can not only make the heavy metals activation and transform into the bioavailable form, bur also can promote the heavy metals transfer into the aboveground parts of plants and improve the efficiency of phytoextraction.In this paper, the remediation of soil of heavy metals sites was studied by adding different chelates oxalic acid, EDTA and EDDS to promote rape remediation of heavy metals contaminated soil, Zn forms in soil would be divided into five parts, included exchangeable(EXC), carbonate bound(CA), Fe-Mn oxide bound (Fe-Mn), organic matter bound(OM) and residual(RES), the effects of different chelate on the form distribution of Zn and soil enzyme activities (urease enzyme, catalase and invertase enzyme) were studied. The correlations between various forms and soil enzyme activity as well as among various forms were also analyzed. The main conclusions are as follows:(1) The effect of different concentrations of oxalic acid treatment on form distribution of Zn in the process of remediation of heavy metals contaminated soil was not obvious, but the effects of different concentrations of EDTA and EDDS treatment on form distribution of Zn in the process of remediation of heavy metals contaminated soil were obvious relatively; the increased amplitudes of the exchangeable Zn were9.28%-48.79%and30.49%-45.08%in the range of experimental concentration, and the optimum concentrations of EDTA and EDDS are both2mmol/kg.(2) The soil activation effects were best in the optimum concentration2mmol/kg of EDTA and EDDS and there was little difference between the effects of EDTA and EDDS. Considering environment friendly, EDDS has more application prospects and EDDS is the optimum chelate.(3) Correlation analysis among five forms of Zn in the condition of different chelate treatments has been studied. It found that in the condition of oxalic acid treatment, the transformation ratios of Fe-Mn and OM were consistent. In the condition of EDTA treatment, the EXC Zn was transformed from CA Zn. In the condition of EDDS treatment, the increased EXC was transformed from CA, Fe-Mn and OM and transformation ratios were consistent.(4) The urease activity was obviously activated and the catalase and invertase activities were all inhibited in different chelates treatments, urease activity can be used as indicator of CA and OM of Zn in soil in the condition of EDDS treatment. Catalase activity can not be used as indicator of any form of Zn in soil. Invertase activity can be used as indicator of RES of Zn in soil in the condition of EDTA treatment. In the condition of EDDS treatment, invertase activity can be used as indicator of five forms of Zn in soil.