Heavy metal contamination is an urgent ecological governance problem in mining areas. In order to seek for a green and environmentally friendly reagent with better plant restoration effect to solve the problem of low efficiency in plant restoration in heavy metal pollution soil. In this study, we evaluated the effects of three biodegradable chelating agents, namely citric acid (CA), fulvic acid (FA) and polyaspartic acid (PASP), on the physicochemical properties of copper tailings, growth of ryegrass (Lolium perenne L.) and heavy metal accumulation therein. The results showed that the chelating agent application improved the physicochemical properties of copper tailings, increased the biomass of ryegrass and enriched more Cu and Cd in copper tailings. In the control group, the main existing forms of Cu and Cd were oxidizable state, followed by residual, weak acid soluble and reducible states. After the CA, FA or PASP application, Cu and Cd were converted from the residual and oxidizable states to the reducible and weak acid soluble states, whose bioavailability in copper tailings were thus enhanced. Besides, the chelating agent incorporation improved the Cu and Cd extraction efficiencies of ryegrass from copper tailings, as manifested by increased root and stem contents of Cu and Cd by 30.29–103.42%, 11.43–74.29%, 2.98–110.98% and 11.11–111.11%, respectively, in comparison with the control group. In the presence of multiple heavy metals, CA, FA or PASP showed selectivity regarding the ryegrass extraction of heavy metals from copper tailings. PCA analysis revealed that the CA-4 and PASP-7 treatment had great remediation potentials against Cu and Cd in copper tailings, respectively, as manifested by increases in Cu and Cd contents in ryegrass by 90.98% and 74.29% compared to the CK group.

Acidification and heavy metal stress pose challenging threats to the terrestrial environment. This investigation endeavors to scrutinize the combined effects of vermicompost and steel slag, either singularly or in concert with Ryegrass (Lolium perenne L.), on the remediation of acidic soil resulting from sulfide copper mining. The findings illuminate substantial ameliorations in soil attributes. The application of these amendments precipitates an elevation in soil pH of 1.39–3.08, an augmentation in organic matter of 4.05–8.65, a concomitant reduction in total Cu content of 43.2–44.7%, and a marked mitigation in Cu bioavailability of 64.2–80.3%. The pronounced reduction in soil Cu bioavailability within the steel slag treatment group (L2) is noteworthy. Characterization analyses of vermicompost and steel slag further elucidate their propensity for sequestering Cu²⁺ ions in the soil matrix. Concerning botanical analysis, the vermicompost treatment group (L1) significantly enhances soil fertility, culminating in the accumulation of 208.35 mg kg⁻¹ of Cu in L. perenne stems and 1412.05 mg kg⁻¹ in the roots. Additionally, the introduction of vermicompost and steel slag enriches soil OTU (Operational Taxonomic Units) quantity, thereby augmenting soil bacterial community diversity. Particularly noteworthy is the substantial augmentation observed in OTU quantities for the vermicompost treatment group (L1) and the combined vermicompost with steel slag treatment group (L3), exhibiting increments of 126.04% and 119.53% in comparison to the control (CK). In summation, the application of vermicompost and steel slag efficaciously diminishes the bioavailability of Cu in the soil, augments Cu accumulation in L. perenne, induces shifts in the soil microbial community structure, and amplifies soil bacterial diversity. Crucially, the concomitant application of vermicompost and steel slag emerges as a holistic and promising strategy for the remediation of sulfide copper mining acidic soil.

The copper sulphide mining process would produce a large number of copper tailings that can be treated with different substrates so as to act as guest soil in the ecological reclamation of the mine. In order to reveal the influence of different copper tailing treatment substrates on plant growth, in this experiment, tall fescue (Festuca arundinacea) was planted under potted conditions for the purpose of exploring the effect of different exogenous substrates such as conditioning agents, sulfurized modified straw, effective microorganisms (EM), and high-density sludge (HDS) sediment on tall fescue height, biomass, chlorophyll, catalase (CAT) activity and Cu²⁺ transport under copper tailings substrate. Then, the results showed that the combined application of different exogenous substrates (conditioning agents, EM, sulfurized modified straw, and HDS sediment) reduced the pH of the copper tailing substrate to varying degrees, with a decrease of 5–21%. Moreover, compared with the control group and other treatments, the combined treatment of conditioning agents, sulfurized modified straw, and EM has a significant impact on the biomass, plant height, chlorophyll content, CAT activity, and other physiological indicators of tall fescue and can effectively reduce Cu²⁺ that is toxic to tall fescue in copper tailing.