To investigate the effects of mushroom residue (SMC) addition on the improvement of gold tailings substrate and plant growth, and to screen plant species with good adaptability and tolerance to gold tailings.

In view of the problems existing in gold tailings, such as extreme nutrient deficiency, poor water and fertilizer retention capacity, unsatisfactory physical structure, excessive accumulation of heavy metals, and the dominance of herbs in existing remediation plants, Koelreuteria paniculata, Nerium oleander, Paulownia fortunei, Rhus typhina, Syringa vulgaris and Acacia podalyriifolia were selected as test plants, and mushroom residue (SMC) was used as the amendment. The physical and chemical properties of three substrates (100% gold tailings as control (CK), 90% tailings + 10% SMC (S1), 80% tailings + 20% SMC (S2)), as well as the differences in physiological and biochemical characteristics, heavy metal uptake and translocation of plants in different substrates were compared.

1) After adding SMC to tailings, the water content increased by 4.21-16.53 percentage points, total porosity increased by 12.39-25.44 percentage points, and organic matter content and cation exchange capacity increased by 66.55%-100.35% and 36.71%-63.24% respectively compared with the control.; 2) Compared with the control group, plants in the amended groups showed better overall performance in growth vigor, biomass, height increment, chlorophyll content, heavy metal uptake and translocation factor; however, there were interspecific differences among plant species within the amended groups; 3) Overall, Paulownia fortunei, Nerium oleander and Koelreuteria paniculata exhibited strong heavy metal tolerance, especially Nerium oleander, which had the best comprehensive performance under S2 treatment. The TOPSIS comprehensive evaluation method was used to comprehensively assess various physiological and biochemical indicators, and it obtained the highest score.

The addition of SMC makes the tailings structure looser and more porous, enhances water permeability and aeration, and effectively improves soil fertility. The growth and development of plants in the amended groups are generally better than those in the control group. Based on comprehensive growth and physiological indicators, Nerium oleander performs the best under S2 treatment (80% tailings + 20% SMC), and can be used as a dominant remediation plant for improved gold tailings.

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.

Arbuscular mycorrhizal fungi (AMF), as a symbiotic fungus of most plants, plays a positive role in the enrichment of heavy metals in plants and the improvement of plant tolerance. In the study, the differences and correlation changes of the spore number and infection rate of arbuscular mycorrhizal fungi on soil related indexes, plant growth indexes, root morphology and soil heavy metal loss in different slag treatment modes were analyzed. The effect of AMF on the ecological interception of four treatment modes was revealed.

With koelreuteria as the main test plant, four treatment groups were designed: CK (100% slag), K0(90% slag +5% mushroom slag +5%CaCO₃), S (Koelreuteria), CP (Koelreuteria + oleander + vetiver), and the experiment was carried out by simulating the mine glass device system.

1) The spore density of AMF soil in four slag treatment modes was CP > S > K0 > CK, and the change trend base of soil porosity, water content and organic matter content in four slag treatment modes was consistent with the change trend of spore number. Urease and phosphatase increased with the increase of amendments and plant planting, and were positively correlated with the number of spores. The general pattern of catalase was CK > K0 > CP > S group, and the difference was significant, and the spore number of AMF was negatively correlated with the four treatment groups. 2) There were significant differences in plant height and biomass between group S and group CP, and AMF in group S was significantly correlated with plant biomass. After compound planting, AMF was significantly correlated with plant height, above-ground biomass and total biomass and extremely significantly correlated with subsurface biomass, and plant root morphology was significantly improved. 3) The pattern of Pb loss was CK > K0 > S > CP, which was negatively correlated with the number of AMF spores. After addition of amendments, soil Pb loss was greatly reduced. After planting koelreuteria the soil loss gradually tended to be stable, and the Zn loss showed a rule of K0 > CK > S > CP. After adding the amendment, the number of spores increased and the loss of Zn was higher than that in the blank group. When planting koelreuteria, the AMF increased significantly, the loss of Zn decreased significantly and the stability increased.

AMF can regulate the pH of soil and positively promote the growth and development of plants. Plant complex planting root system is more complex, can promote the growth and spread of AMF and increase the sharing of nutrients and water between plants, and can penetrate deep into the soil to affect the migration and transformation of Pb and Zn elements. The content of Zn and Pb in plants mainly concentrated in the roots, and the correlation between AMF and Zn and Pb flowing into plants was mainly reflected in stems and leaves. The effect of AMF in the underground part on Zn element was significant. In the growth stage of koelteria, the effect of AMF was mainly reflected in improving the migration and transformation of Zn and transporting it to the stems and leaves above ground, but the effect on Pb element was not obvious.