Rhizosphere effect of different plant patterns on lead-zinc slag remediation

The effect of root effect under different plant planting modes in heavy metal remediation was studied, which laid a theoretical foundation for mine remediation.

An observer-based phytoremediation pilot system of lead-zinc ore was constructed, and the CK group (pure slag control) and S₀ group (modified slag control) were designed to compare the lead-zinc ore restoration effects of single plant system S_Luan (a single tree koelreuteria), S_Jia (a single shrub oleander), S_Xiang (a single herb vetiver), and S_Fu (compound of trees, shrubs and herbs).

(1) After the experiment, compared with the original slag control group, the pH of the plant group was increased by 0.14-0.27, and the water content, porosity, organic matter and cation exchange capacity were increased by 5.3%-9.8%, 9.8%-11.8%, 102.5%-106.9% and 54.2%-66.6%, respectively. The activity of sucrase and urease increased by 130.9%-680.2% and 2.4%-8.6%, respectively. The contents of total nitrogen, total phosphorus and total potassium were increased by 85.5%-115.6%, 0.0%-22.5% and 0.9%-10.5%, respectively. (2) The modifier significantly reduced the amount of Zn loss in the system (P < 0.05). Plant planting significantly decreased the loss of Zn and Pb (P < 0.05), and the loss of Pb and Zn was the lowest under the combination of tree, shrub and grass. Compared with the modified slag control group, the extractable and reducible contents of heavy metal Pb and Zn acid in the plant group were decreased, and the residual Pb in the single tree, single shrub, single herb and shrub compound groups was increased by 6.5%, 5.4%, 11.8% and 6.4%, respectively. Residual Zn increased by 4.0%, 3.4%, 7.9% and 2.1%, respectively. (3) There was little difference in the level of bacterobacteria among different groups. The main dominant bacteria were Proteobacteria, Bacteroidota, Acidobacteriota and so on. At the phylum level, the dominant fungi included Ascomycota, Basidiomycota, Zygomycota, etc.

The addition of amendments improved the soil structure and fertility of the original slag. Amendments and plant planting changed the occurrence forms of Pb and Zn in soil, the residue content was increased. The species abundance of bacteria and fungi was affected by plant planting patterns. The addition of amendments decreased the species richness of fungi in the substrate, while the growth of plants increased the species richness to some extent.