Chapter 13 - Influence of earthworm combined with bermudagrass on the content and bioavailability of heavy metal in reclaimed soil

Abstract

Heavy metal contamination of coal gangue-filled reclaimed soil is one of the reasons that limits the subsequent use of reclaimed land. The reclaimed soil column groups with two different thickness (L group, 50cm) and (H group, 70cm) were set up, and each group included four treatments that were CK (soil without inoculation), E (earthworm inoculation), C (bermudagrass inoculation), and CE (earthworm plus bermudagrass inoculation). The physicochemical properties and behavior of Cr, Cu, Pb, and Zn were analyzed to investigate the effects of earthworm combined with plants on the heavy metals in reclaimed soil. The results showed that different treatments (E, C, and CE) could all reduce the pH, total Cr, Cu, Pb, and Zn contents and increase soil OM, TN, and TP contents in different reclaimed soil column groups. The CE treatment was more effective in reducing total heavy metals contents compared with C and E treatments. The E treatment was able to increase the bioavailability of heavy metals in the soil, while both C and CE treatments decreased the bioavailability of heavy metals. Total Cr, Cu, Pb, and Zn were reduced more significantly in the L group than in the H group. The bioavailability values of Cr and Zn only in CE treatment were reduced lower in H group than those values in the same treatment in L group. Redundancy and correlation analysis indicated that soil pH and OM were the main factors affecting heavy metals behavior in the reclaimed soil. Inoculating earthworms affected the soil pH and OM, which influenced the heavy metals uptake by the bermudagrass. Overall, the study can provide a theoretical basis for the application of earthworms and plants in the remediation of reclaimed soils filled with coal gangue.