Effect of Earthworm-vetiver Combination on Heavy Metals Cr, Cu, Pb and Zn in Reclaimed Soils
- LU Fu-qing, WANG Xing-ming, CHU Zhao-xia, FAN Ting-yu, XU Xiao-ping
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In order to study the effect of earthworm-vetiver combination on the total and available heavy metals (Cr, Cu, Pb, Zn) in reclaimed soils. The soil column simulation experiment was set up for two groups of overburden soil thickness (50 and 70 cm). Each group was set up with four treatments:no vetiver plant without earthworm addition (CK), vetiver plant alone (V), earthworm alone (E) and the combined earthworm-vetiver (VE). The total and available Cr, Cu, Pb and Zn contents and the physicochemical properties of the overburden soil were analyzed for different treatments. The results show that treatments of V, E and VE significantly reduced the total Cr, total Cu, total Pb and total Zn contents of the soil compared to the control (P<0.05). The VE was more effectively in reducing the total amounts of heavy metals than other treatments. The reduction rate of total Cr, total Cu, total Pb and total Zn in VE was 4.90%, 13.12%, 10.36% and 6.91% in the 50 cm group and 5.47%, 11.20%, 10.34% and 6.96% in the 70 cm group, as compared with the CK, respectively. In comparison with CK, treatment E increased the available heavy metals contents, treatment V reduced the available contents of Cu, Pb and Zn, treatment VE showed a weaker reduction for available Pb, but a stronger reduction for available Cu and Zn. At the same thickness, treatments of V, E and VE all reduced pH and increased OM, TN and TP compared to CK. In addition, inoculation with earthworm increased the biomass of vetiver grass, and the root biomass was increased more than shoot biomass. Correlation and redundancy analysis for inoculation with earthworms revealed that, soil pH was significantly and negatively correlated with available Cr and Pb (P<0.05); OM was significantly and negatively correlated with available Cr and Pb and positively correlated with available Zn (P<0.05); TN and TP were significantly negatively correlated with total Cu and total Pb (P<0.05). Soil pH and OM are the key factors affecting soil heavy metal content. Therefore, the combination of earthworm-vetiver can improve physicochemical properties and reduce heavy metal concentration in the reclaimed soil, which provides an important method for the remediation of reclaimed soils.