Method for soilization of iron tailings

Abstract

The application provides a method for soilizing iron tailings, comprising: adding multi-source organic matter material and functional complex microbial flora into the iron tailings to be treated to obtain a primary soil-like substrate; wherein the multi-source organic matter material comprises at least two organic matter materials with different carbon-nitrogen ratios, and the organic matter material comprises plant or livestock and poultry manure; the functional complex microbial flora comprises at least one of lignocellulose-degrading bacteria, nitrogen-fixing bacteria or phosphorus-dissolving bacteria; cultivating a stress-tolerant fine-root plant seedling in a seedling raising substrate to obtain a stress-tolerant fine-root plant; the seedling raising substrate is an inert granular substrate; transplanting the stress-tolerant fine-root plant into the primary soil-like substrate to establish a colony, and adding arbuscular mycorrhizal fungi and sulfur-oxidizing bacteria; and performing water management on the primary soil-like substrate with the stress-tolerant fine-root plant to obtain a soilized active soil-like substrate.

Description

Technical Field

[0001] This application relates to the field of tailings management, and more particularly to a method for soilification of iron tailings. Background Technology

[0002] Iron tailings are solid waste generated after iron ore is crushed, ground, and beneficiated. These tailings, with their unique physical structure and chemical properties, are mainly stored in open pits, forming large-scale tailings dams that reduce land resource utilization. Tailings dams also pose certain safety hazards to the surrounding ecological environment, agricultural product quality, and residents' health. Comprehensive tailings management has become an important issue that needs to be addressed in the fields of environmental science and ecological engineering. Summary of the Invention

[0003] In view of the above, in order to at least partially solve at least one of the aforementioned technical problems, this application provides a method for soilification of iron tailings, comprising the following steps S1 to S4: Step S1: Adding multi-source organic matter materials and functional composite microbial systems to the iron tailings to be treated to cultivate a primary soil-like matrix; wherein, the multi-source organic matter materials include at least two organic matter materials with different carbon-nitrogen ratios, and the organic matter materials include plant or livestock manure; the functional composite microbial system includes at least one of lignocellulose-degrading bacteria, nitrogen-fixing bacteria, or phosphate-solubilizing bacteria. Step S2: Cultivating stress-resistant fine-rooted plant seedlings in a seedling substrate to obtain stress-resistant fine-rooted plants; the seedling substrate is an inert granular substrate. Step S3: Transplanting stress-resistant fine-rooted plants into the primary soil-like matrix and adding arbuscular mycorrhizal fungi and sulfur-oxidizing bacteria. Step S4: Managing the water content of the primary soil-like matrix planted with stress-resistant fine-rooted plants to obtain a soil-like active soil-like matrix.

[0004] According to the embodiments of this application, by adding multi-source organic matter materials and functional composite microbial systems to iron tailings to cultivate a primary soil-like matrix, and then transplanting stress-resistant fine-rooted plant seedlings cultivated in an inert granular matrix, and adding arbuscular mycorrhizal fungi and sulfur-oxidizing bacteria, and finally managing water, iron tailings with poor physical structure and extreme chemical properties can be effectively transformed directly into an active soil-like matrix with soil functions. By simulating a near-natural ecological succession process, through the synergistic effect of organic matter, microorganisms and plants, the alkalinity of tailings is significantly reduced, the organic matter content is increased, the aggregate structure and porosity are improved, and the establishment and growth of plants are promoted, forming a self-sustaining ecosystem, thereby realizing the sustainable soil utilization of iron tailings. Attached Figure Description

[0005] The above and other objects, features and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0006] Figure 1This is a schematic diagram of the process for converting iron tailings into soil in this application;

[0007] Figure 2 This is a comparison diagram of the growth status of each treatment group after 4 months of potted plant experiment in Example 1 of this application;

[0008] Figure 3 This is a comparison diagram of the growth status of each treatment group after 5 months of simulation experiment in Example 2 of this application. Detailed Implementation

[0009] The embodiments of this application will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this application. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of this application for ease of explanation. However, it will be apparent that one or more embodiments may be implemented without these specific details. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0010] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0011] When using expressions such as "at least one of A, B, and C," they should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art.

[0012] In the process of realizing the concept of this application, it was found that the soilification of iron tailings is an important step and a difficult point in the ecological restoration of iron tailings. Its constraint mechanism mainly stems from the significant difference between the matrix characteristics of iron tailings and natural soil. Its physical structure, chemical properties and biological characteristics are extremely poor, and it is a typical "parent material" rather than soil. The main obstacles include: (1) poor physical structure, with a single particle composition, uneven coarseness and fineness, and lack of aggregate structure. Large soil aggregates (diameter 250~2000 µm) account for less than 5%, and small aggregates (diameter 53~250 µm) account for less than 20%, resulting in low porosity, poor aeration and water permeability, and easy surface compaction. (2) extreme chemical properties, strong alkalinity, high salinity, pH value > 9.5, lack of organic matter and usable nutrients, total organic carbon concentration < 0.1 g / kg, and extremely low content of essential plant nutrients such as nitrogen, phosphorus and potassium, especially nitrogen, which can hardly meet the growth needs of plants. (3) Lack of biological activity, lack of soil microorganisms and animal communities, inability to start ecosystem functions, interruption of material cycle and energy flow.

[0013] The ecological restoration of iron tailings mainly relies on the following technologies: (1) Topsoil covering method: directly covering the tailings surface with fertile soil. Although this method is effective, it is extremely expensive, consumes valuable topsoil resources, and the topsoil layer and the underlying tailings are prone to forming a water-impermeable layer, causing geological disasters such as landslides. It is not a sustainable solution. (2) Chemical amendment method: applying large amounts of chemical fertilizers, organic fertilizers or soil conditioners. This method can improve fertility in the short term, but it fails to solve structural problems. Long-term use of large amounts can easily cause secondary pollution, and the cost is also high. (3) Single plant remediation: directly planting tolerant plants. Since the tailings substrate itself does not have the ability to support the long-term growth of plants, the plants often grow poorly, the community degrades, and the remediation effect is unstable. (4) Microbial remediation method: improving the tailings substrate by inoculating functional microorganisms (such as nitrogen-fixing bacteria or phosphate-solubilizing bacteria). This method has obvious artificial community characteristics, single and fragile ecological functions, and is easily damaged.

[0014] It can be seen that related technologies often overlook the direct chemical damage to seedling roots caused by the high alkalinity of tailings, and lack dynamic microbial regulation strategies for the soil formation process of tailings with different weathering degrees.

[0015] Figure 1 This is a schematic diagram of the process for converting iron tailings into soil in this application.

[0016] Based on this, according to one embodiment of this application, a method for iron tailings soilification is provided, such as... Figure 1 As shown, it includes the following steps S1 to S4:

[0017] Step S1: Add multi-source organic matter materials and functional composite microbial systems to the iron tailings to be treated, and cultivate them to obtain a primary soil-like matrix; wherein, the multi-source organic matter materials include at least two kinds of organic matter materials with different carbon-nitrogen ratios, and the organic matter materials include plant or livestock and poultry manure; the functional composite microbial systems include at least one of lignocellulose degrading bacteria, nitrogen-fixing bacteria or phosphate-solubilizing bacteria.

[0018] Step S2: Cultivate stress-tolerant fine-rooted plant seedlings in the seedling substrate to obtain stress-tolerant fine-rooted plants; the seedling substrate is an inert granular substrate.

[0019] Step S3: Transplant stress-tolerant fine-rooted plants into the primary soil matrix and add arbuscular mycorrhizal fungi and sulfur-oxidizing bacteria.

[0020] Step S4: Perform water management on the primary soil-like substrate planted with stress-tolerant fine-rooted plants to obtain a soil-like active soil-like substrate.

[0021] According to the embodiments of this application, by adding multi-source organic matter materials and functional composite microbial systems to iron tailings to cultivate a primary soil-like matrix, and then transplanting stress-resistant fine-rooted plant seedlings cultivated in an inert granular matrix, and adding arbuscular mycorrhizal fungi and sulfur-oxidizing bacteria, and finally managing water, iron tailings with poor physical structure and extreme chemical properties can be effectively transformed directly into an active soil-like matrix with soil functions. By simulating a near-natural ecological succession process, through the synergistic effect of organic matter, microorganisms and plants, the alkalinity of tailings is significantly reduced, the organic matter content is increased, the aggregate structure and porosity are improved, and the establishment and growth of plants are promoted, forming a self-sustaining ecosystem, thereby realizing the sustainable soil utilization of iron tailings.

[0022] Furthermore, the iron tailings soilification method of this application specifically manifests as follows: after one growth cycle, the total organic carbon content in the surface layer (0~20 cm) of the iron tailings is increased by more than 20 times (reaching more than 10 g / kg), the proportion of water-stable aggregates of 0.25~2 mm is increased by more than 5 times (reaching more than 30%), the porosity of the iron tailings is increased by more than 1 times (reaching more than 35%), and the pH value is reduced by at least 2.4 units (reaching below 7.3).

[0023] In one or more embodiments of this application, step S1 further includes mechanically crushing the plant material in the multi-source organic material to a length of 2-5 cm to increase the specific surface area and promote microbial degradation and mixing with the matrix.

[0024] In one or more embodiments of this application, in step S1, the multi-source organic material is applied by uniformly spreading the mixed organic matrix on the leveled iron tailings surface, with an application rate of 5~15 kg / m³. 2 Preferably, it is 8~12 kg / m2 Then, a one-time shallow tillage and mixing process with a depth of 20-30 cm is carried out. The crushed grass straw is used as a durable physical support framework. Unlike easily decomposed organic fertilizer, a certain length of straw fiber is retained to build a three-dimensional network pore structure on the surface of the tailings. This effectively prevents the tailings from hardening after irrigation, ensures continuous oxygen supply, and provides a guarantee for the survival of aerobic microorganisms (nitrogen-fixing bacteria and fungi) until the root network of pioneer plants is formed.

[0025] According to the embodiments of this application, at least one of the following conditions is met: (1) the amount of multi-source organic material added is 5~15 kg / m³. 2 (2) The carbon-nitrogen ratio of the multi-source organic matter material is (20~30):1; (3) The plants in the organic matter material include grass straw and leguminous plant material, and the leguminous plant material is leguminous plant residue or litter; (4) The inert particle matrix is ​​chemically inert porous particles, including at least one of natural river sand, quartz sand, perlite, ceramsite, and biochar.

[0026] According to an embodiment of this application, in step S1, the amount of multi-source organic material added can be 5 kg / m³. 2 8kg / m 2 10 kg / m 2 12 kg / m 2 15 kg / m 2 However, this is not limited to the listed values; other unlisted values ​​within this range also apply. Or, it can be a range consisting of any two values, such as 8–12 kg / m³. 2 5~10 kg / m 2 wait.

[0027] According to the embodiments of this application, the amount of multi-source organic matter added can ensure that the necessary organic carbon and nutrient basis for iron tailings conversion is provided in an economical and optimal dosage, ensuring that the intensity of microbial activity and the matrix improvement effect reach the best balance, avoiding poor effect due to insufficient addition or waste of resources and potential ecological risks due to excessive addition.

[0028] According to an embodiment of this application, in step S1, the carbon-nitrogen ratio of the multi-source organic material can be 20:1, 22:1, 24:1, 26:1, 28:1, or 30:1, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. Alternatively, it can be within a range consisting of any two values, such as (20~25):1, (22~36):1, etc.

[0029] According to embodiments of this application, a suitable carbon-nitrogen ratio in multi-source organic matter materials can drive microorganisms (especially functional composite microbial systems) to carry out efficient decomposition and humification, while promoting the transformation of organic matter into stable humus, thereby rapidly and continuously improving substrate fertility and structure.

[0030] In one or more embodiments of this application, in step S1, the multi-source organic material includes grass straw and leguminous material.

[0031] Specifically, grass straw includes at least one of corn straw, wheat straw, or rice straw, and the carbon-to-nitrogen ratio of the grass straw is (20~50):1. The carbon-to-nitrogen ratio of grass straw can be 20:1, 30:1, 40:1, or 50:1, but is not limited to the listed values; other unlisted values ​​within this range also apply. Alternatively, it can be within a range consisting of any two values, such as (20~30):1, (40~50):1, etc.

[0032] Specifically, leguminous plant materials include at least one of the plant residues or green manure from alfalfa, white clover, soybean, and pea, with a carbon-to-nitrogen ratio of (10~30):1. The carbon-to-nitrogen ratio of leguminous plant materials can be 10:1, 20:1, or 30:1, but is not limited to the listed values; other unlisted values ​​within this range also apply. Alternatively, it can be within any range of two values, such as (20~30):1, (40~50):1, etc.

[0033] In one or more embodiments of this application, in step S1, the multi-source organic material further includes mushroom residue. Based on the total mass of the multi-source organic material, the mass ratio of livestock and poultry manure and mushroom residue is 5% to 20%. The mass ratio of livestock and poultry manure and mushroom residue can be 5%, 10%, 15%, or 20%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. Or it can be within a range consisting of any two values, such as 5% to 10%, 15% to 20%, etc.

[0034] In one or more specific embodiments of this application, the carbon-nitrogen ratio of the multi-source organic matter material can be obtained by mixing grass straw and leguminous plant materials with different carbon-nitrogen ratios in a certain proportion, so that the carbon-nitrogen ratio of the multi-source organic matter material is (20~30):1.

[0035] In one or more specific embodiments of this application, the mass ratio of grass straw to leguminous material can be (0.5~5):1, preferably (1~3):1, so that the carbon-nitrogen ratio of the mixed organic matrix is ​​stabilized at (20~30):1.

[0036] Specifically, when one or more of livestock and poultry manure, mushroom residue, and sludge compost are added, the amount of leguminous plant material is reduced accordingly to maintain the target carbon-nitrogen ratio range.

[0037] According to the embodiments of this application, by utilizing the highly structured carbon source provided by gramineous straw and the abundant nitrogen source provided by leguminous straw, nitrogen-fixing bacteria synergistically solve the bottleneck of extreme nitrogen deficiency in iron tailings. The high-structured carbon source and leguminous straw synergistically introduce diverse organic components, simulating the organic matter composition of natural soil and enhancing the biodiversity carrying capacity of the matrix. Gramineous straw provides a physical framework and carbon source, improving the pore structure of the matrix; leguminous materials provide easily decomposable nitrogen source. The mixture of the two provides a balanced supply of nutrients and organic carbon to the iron tailings matrix, effectively improving the physical structure of the matrix, increasing porosity and aggregate stability, and initiating biochemical evolution, laying the foundation for subsequent pioneer plant colonization and microbial coupling.

[0038] According to embodiments of this application, the stress-tolerant fine-rooted plant is a grass, preferably one or more of foxtail grass, crabgrass, ryegrass, or sorghum; the stress-tolerant fine-rooted plant seedlings are planted in a primary soil-like substrate at a planting density of 7-20 plants / m². 2 .

[0039] According to the embodiments of this application, gramineous plants (especially foxtail, crabgrass, ryegrass, or sorghum) possess the core capabilities for survival and reproduction in the extreme environment of iron tailings, namely, a well-developed fine root system, strong tolerance to poor soil and alkali, and rapid growth, thereby effectively establishing themselves and playing the ecological function of pioneer plants. Appropriate planting density can form a sufficiently dense and uniform root network per unit area, creating an efficient coupling effect with the organic matter and functional microorganisms in the primary soil-like matrix. This achieves both effective penetration, binding, and stabilization of matrix particles, promoting the formation of water-stable aggregates, and continuous provision of active substrates for microorganisms through root exudates and shed material, driving the biochemical improvement of the matrix. Simultaneously, it avoids the problems of excessive resource competition due to overly dense planting or insufficient cover due to overly sparse planting, achieving efficient and uniform occupation and improvement of matrix space in the early stages of remediation. This lays a solid vegetation foundation for the subsequent self-sustaining and succession of the ecosystem, thus ensuring the success rate of the entire iron tailings soilification process and the stability of the final remediation effect.

[0040] In one or more embodiments of this application, in step S3, stress-tolerant fine-rooted plants are transplanted into a primary soil-like substrate without root washing, so as to preserve the inert granular substrate adhering to the roots to protect the rhizosphere microenvironment and introduce the rhizosphere effect.

[0041] Furthermore, the fibrous skeleton of straw, along with the interpenetration of pioneer plant roots and rhizosphere microorganisms such as mycorrhizal fungi and sulfur-oxidizing bacteria, effectively broke down the tailings crust, stimulated mineral weathering, and increased porosity and aeration and permeability. In particular, the rhizosphere sand particles retained during transplanting, together with the extracellular polysaccharides and humus secreted by microorganisms, acted as the core cementing agent for aggregates, significantly promoting the formation of matrix aggregate structure.

[0042] Specifically, the inert granular matrix consists of specific chemically inert porous particles, such as natural river sand and quartz sand, which ensures the physical stability and chemical safety of the seedling substrate. The chemical inertness avoids chemical interference to the roots during the seedling stage, and its porosity provides an ideal physical protection and gas exchange environment for the roots. It effectively isolates the initial stress of highly alkaline tailings, which can improve the survival rate and transplant adaptability of pioneer plant seedlings and provide preferential colonization sites for subsequent inoculation of rhizosphere microorganisms.

[0043] According to an embodiment of this application, in step S1, the effective viable count in the functional composite microbial system is greater than or equal to 1.0 × 10⁻⁶. 8 The CFU / g ensures that a sufficient amount of active microorganisms are introduced into the primary soil-like matrix, which can quickly initiate and dominate the decomposition and transformation process of organic matter, overcoming the initial biological inhibition of the tailings environment.

[0044] According to the embodiments of this application, the functional compound microbial system can be a premixed compound microbial agent, or it can be a mixture of various functional microbial agents on site or inoculated in multiple times. This application does not impose any restrictions on this.

[0045] In one or more embodiments of this application, the nitrogen-fixing bacteria are either Rhizobium or Nitrogenobacterium.

[0046] In one or more embodiments of this application, the phosphate-solubilizing bacteria are Pseudomonas or Bacillus.

[0047] In one or more embodiments of this application, the lignocellulose-degrading bacteria are Trichoderma.

[0048] In one or more embodiments of this application, the arbuscular mycorrhizal fungus is of the genus *Glomus*, and the number of spores of the arbuscular mycorrhizal fungus is >30 / g.

[0049] In one or more embodiments of this application, the sulfur-oxidizing bacteria are multifunctional bacteria, and the effective viable count of the sulfur-oxidizing bacteria is greater than or equal to 1.0 × 10⁻⁶. 8 CFU / g.

[0050] Specifically, biological nitrogen fixation increases nitrogen sources, activates insoluble phosphorus to enhance phosphorus availability, and efficiently degrades stubborn lignocellulose in straw-like organic matter to promote humification. The aforementioned fungi have advantages in environmental tolerance, metabolic efficiency, and functional complementarity. Their combination can synergistically act on iron tailings substrate, rapidly converting the added multi-source organic matter into usable nutrients and cementing substances that form soil structure, thereby accelerating the cultivation process of primary soil-like substrate and creating a more nutritionally balanced and biologically active microenvironment for subsequent plant planting.

[0051] In one or more embodiments of this application, the inoculation sequence of the functional composite microbial system is as follows: first, lignin and cellulose degrading bacteria are inoculated to promote the initial decomposition of organic residues, and then nitrogen-fixing bacteria and phosphate-solubilizing bacteria are inoculated to promote nutrient accumulation.

[0052] In one or more embodiments of this application, the inoculation method for the functional composite microbial system is spraying with an aqueous suspension or mixing with a dry carrier and spreading.

[0053] According to the embodiments of this application, the inoculum size of the functional complex microbial system is 100~200 g / m³. 2 .

[0054] According to embodiments of this application, the inoculum size of the functional composite microbial system can be 100 g / m³. 2 150 g / m 2 200 g / m 2 However, this is not limited to the listed values; other unlisted values ​​within this range also apply. Or, it can be a range consisting of any two values, such as 100~150 g / m³. 2 120~180 g / m 2 150~200 g / m 2 wait.

[0055] According to the embodiments of this application, the inoculation amount of the functional composite microbial system can ensure the minimum and optimal dose of effective biological activity of microorganisms in iron tailings per unit area, which can ensure that a sufficient number of functional bacteria occupy the main position and improve the matrix in the early stage, while avoiding resource waste and potential ecological risks.

[0056] In one or more embodiments of this application, the functional complex microbial strain is prepared at a concentration of 100-200 g / m³. 2 Preferred concentration: 120~180 g / m 2 The inoculation amount is added to the iron tailings by spraying with water suspension or by mixing with dry carrier and spreading, and then mixed with the iron tailings matrix by shallow tillage and mixing at a depth of 20~30 cm.

[0057] According to the embodiments of this application, based on the effective viable bacteria count, the ratio of lignocellulose-degrading bacteria: nitrogen-fixing bacteria: phosphate-solubilizing bacteria in the functional composite microbial system is 1:(0.1~10):(0.1~10), preferably 1:(0.5~5):(0.5~5).

[0058] In one or more embodiments of this application, the ratio of lignocellulose-degrading bacteria: nitrogen-fixing bacteria: phosphate-solubilizing bacteria in the functional composite microbial system is 1:(0.5~5):(0.5~5), based on the effective viable bacteria count.

[0059] In one or more embodiments of this application, the ratio of lignin and cellulose degrading bacteria, nitrogen-fixing bacteria, and phosphate-solubilizing bacteria can be dynamically adjusted according to the weathering degree of iron tailings.

[0060] For example, for fresh, unweathered tailings (with extremely high C / N ratio and extremely poor structure), it is preferable to increase the ratio of lignin and cellulose degrading bacteria (e.g., 1:0.5:0.5) to accelerate straw softening and organic acid release; for extremely barren, long-weathered tailings, it is preferable to increase the ratio of nitrogen-fixing bacteria to phosphorus-solubilizing bacteria (e.g., 1:5:5) to enhance nutrient accumulation; a general strategy, i.e., a balanced ratio of 1:1:1 to 1:2:2, can also be used.

[0061] According to embodiments of this application, based on the effective viable bacteria count, the ratio of lignocellulose-degrading bacteria: nitrogen-fixing bacteria: phosphate-solubilizing bacteria in the functional composite microbial system can be 1:0.1:10, 1:10:0.1, 1:5:10, 1:10:5, 1:1:10, 1:8:5, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. Alternatively, it can be within a range consisting of any two values, such as 1:(0.1~10):(0.1~10), 1:(0.1~10):(0.1~10), etc.

[0062] According to the embodiments of this application, the ratio of lignocellulose-degrading bacteria, nitrogen-fixing bacteria, and phosphate-solubilizing bacteria ensures a highly efficient dynamic balance in the number of these three types of functional microorganisms. This avoids the excessive dominance of a single microbial community that could inhibit other functions, while ensuring that the three biochemical processes of organic matter decomposition, nitrogen fixation, and phosphorus activation can proceed synchronously and in a coordinated manner. This improves the conversion efficiency of organic matter and the rate of nutrient release, thereby enhancing the cation exchange capacity (CEC) and fertilizer retention capacity of the iron tailings to be treated through the mineralization and decomposition of organic materials. Simultaneously, the lignocellulose-degrading bacteria, nitrogen-fixing bacteria, phosphate-solubilizing bacteria, and pioneer plants construct a primary food web, increasing the biomass and diversity of the substrate microorganisms and activating the previously dormant ecological functions of the tailings.

[0063] According to an embodiment of this application, in step S3, the inoculation amount of arbuscular mycorrhizal fungi is 100~200 g / m². 2The inoculum size for sulfur-oxidizing bacteria is 10-15 mL / m³. 2 .

[0064] According to embodiments of this application, the inoculation amount of arbuscular mycorrhizal fungi can be 100 g / m². 2 150 g / m 2 200 g / m 2 However, this is not limited to the listed values; other unlisted values ​​within this range also apply. Or, it can be a range consisting of any two values, such as 100~150 g / m³. 2 120~200 g / m 2 wait.

[0065] According to the embodiments of this application, the inoculum size of sulfur-oxidizing bacteria can be 10 mL / m 2 12 mL / m 2 14 mL / m 2 15mL / m 2 However, this is not limited to the listed values; other unlisted values ​​within this range also apply. Or, it can be a range consisting of any two values, such as 10–12 mL / m 2 13~14 mL / m 2 wait.

[0066] According to embodiments of this application, the inoculation amount of arbuscular mycorrhizal fungi ensures sufficient fungal propagules (such as spores and hyphal fragments) to fully contact plant roots, enabling efficient inoculation of plant roots in barren environments like iron tailings. The fungi form a symbiotic network with plant roots, aiming to physically entangle particles to promote aggregate formation and expand the root system's absorption range of phosphorus and water. Sulfur-oxidizing bacteria promote mineral weathering and secondary mineral formation in tailings, thereby promoting organic-mineral interactions and aggregate structure formation.

[0067] According to the embodiments of this application, the inoculation amount of sulfur-oxidizing bacteria is regulated to address the high alkalinity of iron tailings, ensuring sufficient formation of a powerful microbial community in the rhizosphere region to continuously and efficiently neutralize the alkalinity of the substrate by oxidizing sulfur to produce sulfuric acid.

[0068] According to the embodiments of this application, the dosage of arbuscular mycorrhizal fungi and sulfur-oxidizing bacteria is matched to achieve synergistic effects of biological neutralization and biological nourishment. That is, sulfur-oxidizing bacteria rapidly improve the pH environment of the rhizosphere microdomain, removing chemical barriers for the survival and function of plants and arbuscular mycorrhizal fungi; while arbuscular mycorrhizal fungi enhance plant health, and their root exudates can provide carbon sources for sulfur-oxidizing bacteria and other microorganisms, maintaining their activity.

[0069] Furthermore, this application constructs a dual acid-producing pathway to synergistically reduce the substrate pH: on the one hand, the inoculated sulfur-oxidizing bacteria utilize trace amounts of reduced sulfur (such as pyrite particles) contained in the tailings themselves or sulfur sources carried in organic materials to oxidize and produce acid; on the other hand, humic acid and organic acids produced in the early stage of organic matter fermentation are continuously released. The two work synergistically to efficiently neutralize the strong alkalinity of the iron tailings (from pH above 9.0 to below 7.5).

[0070] According to the embodiments of this application, the cultivation time for primary soil-like substrate is 15 to 60 days, preferably 25 to 35 days; the seedling cultivation time for stress-tolerant fine-rooted plants is 20 to 40 days.

[0071] According to the embodiments of this application, the cultivation time of the primary soil-like substrate and the cultivation time of the stress-resistant fine-rooted plant seedlings provide a suitable time window for the entire biotransformation and plant physiological process. The cultivation time range of the primary soil-like substrate ensures that the functional composite microorganisms have enough time to complete the full decomposition and humification of multi-source organic matter and the initial improvement of the substrate, while avoiding the reduction in efficiency caused by an excessively long cultivation cycle. The seedling cultivation time ensures that the plant roots can fully develop in the inert granular substrate and form a root ball carrying protective particles, achieving the best transplanting physiological state.

[0072] Specifically, the coordinated control of two time parameters enables the improvement of the physicochemical and biological properties of the primary soil-like substrate to be completed simultaneously with the physiological development of the seedlings, allowing for transplanting and planting. This maximizes the interaction efficiency between the plants and the improved substrate, laying the foundation for subsequent deep coupling.

[0073] According to an embodiment of this application, in step S4, the water management period is 1 to 2 growth cycles.

[0074] According to embodiments of this application, in 1-2 water management practices, a close mutualistic symbiotic relationship can be fully established between plants and introduced rhizosphere microorganisms, enhancing the system's nutrient internal circulation and self-sustaining capacity. Through this process, the organic matter content, water-stable aggregates, and porosity of the iron tailings matrix are significantly increased, ultimately transforming it into an active soil-like matrix.

[0075] The following will further explain the solution of this application through specific embodiments. Unless otherwise specified, all reagents used are commercially available reagents, and all test methods or experimental methods used are conventional experimental methods in the art.

[0076] Example 1: Small Potted Plant Verification Experiment

[0077] 1. Materials and Methods

[0078] Tailings tested: Taken from an iron tailings pond in Baoding, Hebei Province, air-dried and passed through a 2 mm sieve. Basic properties: pH = 9.7, total organic carbon = 0.48 g / kg, total nitrogen = 0.38 g / kg. The tailings contain 1%–3% pyrite-like minerals.

[0079] Experimental Design:

[0080] A completely randomized design was used, with a total of 4 treatment groups and 4 biological replicates for each treatment (n = 4).

[0081] The processing settings are as follows:

[0082] CK (control group): Untreated iron tailings without any additives.

[0083] T1 (Organic Matter Treatment): Iron tailings + organic matter (grass straw and leguminous plant residues, addition ratio: 2% w / w).

[0084] T2 (Microbial Treatment): Iron tailings + composite microbial system (effective viable count ≥ 1.0 × 10⁻⁶) 8 CFU / g, inoculum size: 150 g / m² 2 ).

[0085] T3 (Combined Treatment): Iron tailings + organic matter + composite microbial system (inoculum size: 150 g / m³) 2 ).

[0086] 2. Substrate pre-culture

[0087] Before the experiment began, the air-dried and sieved (2 mm) iron tailings were weighed and placed into the experimental container (size: 16 × 17.5 cm, soil content per container: 2 kg).

[0088] Based on the experimental design described above, organic matter and microbial agents were added to the substrates of the corresponding treatments, respectively. To ensure uniformity, the amendment and tailings were thoroughly mixed using mechanical stirring. Deionized water was added to all treatments (including the control group) to adjust the substrate moisture content to 60%–70% of field capacity.

[0089] The treated substrate was placed in a greenhouse for a one-month pre-cultivation period to stabilize its physicochemical properties and allow for microbial colonization. During the pre-cultivation period, greenhouse conditions were controlled at a day / night temperature of 25±2 ℃ / 18±2 ℃ and a relative humidity of approximately 60%. A breathable covering (such as a perforated film) could be used on the substrate surface to reduce moisture evaporation and prevent external contamination. Deionized water was added every three days using a weighing method to maintain the moisture content at 60%–70% of field capacity. If necessary, the substrate was lightly turned over weekly to ensure aeration and mixing.

[0090] 3. Plant seedling cultivation

[0091] Simultaneously with substrate pre-culture, seedling cultivation of the test plants was carried out. Maize was selected as the indicator plant. Cleaned and sterilized river sand was used as the seedling substrate to ensure root integrity and preservation of rhizosphere characteristics during later transplanting. Seeds were surface-sterilized (soaked in 10% H2O2 for 10 minutes) and then sown in seedling trays filled with sand. Seeds were cultivated for one month under growth chamber conditions (light / dark: 14 h / 10 h, temperature: 25℃ / 20℃). During this period, seedlings were regularly irrigated with 1 / 2 Hoagland nutrient solution to ensure normal seedling growth.

[0092] 4. Transplanting and Cultivation

[0093] After one month of substrate pre-culture and one month of plant seedling cultivation, transplanting is carried out. The fine-rooted pioneer plant seedlings from the sand culture are carefully removed. To protect the rhizosphere microenvironment and introduce the rhizosphere effect, the rhizosphere sand adhering to the roots is retained; root washing is not performed. Healthy seedlings with uniform growth are selected and transplanted into the pre-cultured iron tailings substrate for each treatment. Three seedlings are planted per pot. Simultaneously, arbuscular mycorrhizal fungi inoculum (inoculation rate: 150 g / m³) is applied. 2 (50 spores / g) and sulfur-oxidizing bacteria (effective viable count ≥ 1.0 × 10⁻⁶). 8 CFU / mL, inoculation volume 10ml / m 2 The substrate was added to the iron tailings substrate via broadcasting and spraying. After transplanting, all experimental pots were randomly placed in a greenhouse for a four-month growth and cultivation period. During cultivation, natural light (or supplemental lighting up to 14 hours) was provided, day / night temperatures were controlled at 25 / 18 ℃, and relative humidity was maintained at approximately 60%. Deionized water was added regularly to maintain substrate moisture, and no additional chemical fertilizers were applied to assess the fertility supply capacity of the improved substrate.

[0094] 5. Results Analysis

[0095] After cultivation, the physicochemical properties of the substrate and plant growth indicators were measured, and the results are shown in Table 1 below. Figure 2 As shown.

[0096] Figure 2 This is a comparison chart of the growth status of each treatment group after 4 months of potted plant experiment in Example 1 of this application.

[0097] Table 1. Changes in the physicochemical and biological properties of tailings in a pot experiment (120 days)

[0098]

[0099] Note: The data in Table 1 are the mean of four replicates.

[0100] According to Table 1 and Figure 2It can be seen that T3 (the complete treatment scheme) exhibits significant advantages. Compared with CK, the total organic carbon content increased by more than 20 times, the total nitrogen content increased by approximately 234.2%, the proportion of large water-stable aggregates increased by approximately 5 times, the iron tailings changed from extremely alkaline to neutral, and plant growth was vigorous. This indicates that the soilification method provided in this application can significantly accelerate the soilification process of iron tailings.

[0101] It is worth noting that the significant decrease in pH value in the T3 treatment group (9.7 > 7.3) was due to the synergistic effect of sulfur-oxidizing bacteria and organic acids. In the early stage of the experiment, organic acids rapidly neutralized some of the alkalinity; in the later stage, sulfur-oxidizing bacteria continuously oxidized trace amounts of sulfide minerals in the tailings, preventing pH from rising again and ensuring a long-lasting improvement effect.

[0102] Example 2: Greenhouse area simulation experiment of real iron tailings

[0103] 1. Materials and Methods

[0104] The iron tailings sourced was consistent with that in Example 1, originating from an iron tailings dam in Baoding, Hebei Province. After natural air drying, the substrate was sieved through a 2mm sieve to remove large stones and gravel. Simulated experimental zones were established in a greenhouse using plastic boxes measuring 0.56 m × 0.42 m × 0.26 m (length × width × height). Each simulated zone was filled with 20 kg of the tested iron tailings, with a filling thickness of approximately 19 cm, to simulate the surface soil environment of a real iron tailings dam.

[0105] 2. Experimental Design

[0106] This embodiment also employs a completely randomized design, setting up 4 treatment groups, with each treatment having 4 replicate blocks (a total of 16 blocks). The treatment settings are as follows:

[0107] CK (control group): Untreated iron tailings without any additives.

[0108] T1 (Organic Matter Treatment): Iron tailings + organic matter. The organic matter is a mixture of grass straw (corn straw) and leguminous plant residues (alfalfa powder) in a certain proportion, and the amount added is 2% of the dry weight of the substrate (i.e., 2 kg of organic matter is added to each block).

[0109] T2 (Microbial Treatment): Iron tailings + composite microbial system. Inoculum amount calculated by area, using arbuscular mycorrhizal fungi inoculum (inoculum amount 150 g / m²). 2 (50 spores / g) and sulfur-oxidizing bacteria (effective viable count ≥ 1.0 × 10⁻⁶). 8 CFU / mL, inoculation volume 10ml / m 2 ).

[0110] T3 (Combined Treatment): Iron tailings + organic matter (2 kg / block) + composite microbial system (the composite microbial system is the same as T2).

[0111] 3. Experimental Procedure

[0112] (1) Step 1: Substrate pre-culture

[0113] Before the experiment, the surface of the iron tailings in each simulated block was leveled. According to the experimental design, the weighed organic matter and compound microbial agent were evenly spread on the tailings surface corresponding to the treatment. Shallow tillage to a depth of 8–11 cm was performed using a manual shovel to ensure thorough mixing of the amendment with the surface tailings, constructing an artificial composite layer. Deionized water was sprayed onto all blocks (including the control group) to adjust the substrate moisture content to 60%–70% of field capacity. Subsequently, a static pre-cultivation period of one month was conducted under greenhouse conditions, during which moisture was monitored every 3–5 days and water was added as needed to induce microbial colonization and the initial evolution of the substrate's physicochemical properties.

[0114] (2) Step Two: Plant Seedling Cultivation

[0115] During the same period of substrate pre-culture, plant seedlings were cultivated. Corn was selected as the indicator plant. Cleaned and sterilized coarse river sand was used as the seedling substrate. Seeds were surface-sterilized with 10% H2O2 for 10 minutes and then germinated before being sown in seedling trays filled with river sand. The seedlings were cultivated for one month under growth chamber conditions (light / dark: 14 h / 10 h, temperature: 25℃ / 20℃). During this period, the seedlings were regularly watered with 1 / 2 Hoagland nutrient solution to cultivate robust seedlings with well-developed root systems and abundant rhizosphere sand.

[0116] (3) Step 3: Transplanting and Planting

[0117] After one month of pre-culture in the substrate and one month of seedling growth, transplanting is carried out. Carefully remove the sand-cultured seedlings, ensuring the sand adhering to the roots is intact; root washing is strictly prohibited to protect the rhizosphere microenvironment and promote pioneer plant establishment. Transplant the seedlings to their respective simulated blocks at a planting density of 8-10 plants / m². 2 (Adjust row spacing according to plant size, maintaining uniform row spacing). At the same time as transplanting, inoculate with arbuscular mycorrhizal fungi (inoculation amount: 150 g / m²). 2 (spore count ≥ 30 / g) and sulfur-oxidizing bacteria (effective viable count ≥ 1.0 × 10⁻⁶). 8 CFU / mL, inoculum volume 10mL / m 2 Apply the solution to the soil surface around the plant roots by broadcasting or spraying, then cover with soil, compact, and water thoroughly.

[0118] (4) Step Four: Cultivation and Management Environment Control

[0119] After transplanting, a four-month growth trial was conducted. The greenhouse environment was controlled as follows: natural light (supplemented to 14 hours if necessary), day / night temperature of 25℃ / 18℃, and relative humidity of approximately 60%. An automatic sprinkler or drip irrigation system was installed, and deionized water was regularly added to maintain substrate moisture. The application of any chemical fertilizers was strictly prohibited throughout the entire process to force the plants to establish a symbiotic relationship with the introduced functional microorganisms, thereby assessing the improved substrate's ability to supply endogenous nutrients for plant growth and its soil-like properties.

[0120] 4. Results Analysis

[0121] The physicochemical properties of the tailings in the greenhouse area are shown in Table 2 below. Figure 3 As shown.

[0122] Figure 3 This is a comparison chart of the growth status of each treatment group after 5 months of simulation experiment in Example 2 of the present invention.

[0123] Table 2. Physicochemical properties of tailings and plant growth indicators in the greenhouse area (150 days)

[0124]

[0125] According to Table 2 and Figure 3 It can be seen that the greenhouse pilot experiment further verified the effectiveness of the soilification method of this application. After 150 days of cultivation, the tailings matrix under the T3 treatment has improved in terms of organic matter, structure, biodiversity and vegetation productivity. The matrix has initially shown the rudiments of soil, providing solid data support for the large-scale application of real iron tailings.

[0126] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for soilification of iron tailings, comprising: Multi-source organic matter materials and functional composite microbial systems are added to iron tailings to be treated to cultivate a primary soil-like matrix; wherein, the multi-source organic matter materials include at least two organic matter materials with different carbon-nitrogen ratios, and the organic matter materials include plant or livestock manure; the functional composite microbial system includes at least one of lignocellulose-degrading bacteria, nitrogen-fixing bacteria, or phosphate-solubilizing bacteria; Seedlings of stress-tolerant fine-rooted plants are cultivated in a seedling substrate to obtain stress-tolerant fine-rooted plants; the seedling substrate is an inert granular substrate. Transplant the stress-resistant fine-rooted plants into the primary soil-like substrate and add arbuscular mycorrhizal fungi and sulfur-oxidizing bacteria; Water management was applied to the primary soil matrix planted with the aforementioned stress-tolerant fine-rooted plants to obtain a soil-like active soil matrix.

2. The method according to claim 1, wherein, At least one of the following conditions must be met: (1) The amount of the multi-source organic material added is 5~15 kg / m³. 2 ; (2) The carbon-to-nitrogen ratio of the multi-source organic material is (20~30):1; (3) The plants in the organic material include grass straw and leguminous plant material, wherein the leguminous plant material is leguminous plant residue or litter; (4) The inert particle matrix is ​​a chemically inert porous particle, including at least one of natural river sand, quartz sand, perlite, ceramsite, and biochar.

3. The method according to claim 2, wherein, The gramineous plant straw includes at least one of corn straw, wheat straw, or rice straw, and the carbon-to-nitrogen ratio of the gramineous plant straw is (20~50):1; The legume material includes at least one of the plant residues or green manure of alfalfa, white clover, soybean, and pea, and the carbon-nitrogen ratio of the legume material is (10~30):

1.

4. The method according to claim 1, wherein, The organic material also includes bacterial residue; Based on the total mass of the multi-source organic matter materials, the mass ratio of livestock and poultry manure and fungal residue is 5% to 20%.

5. The method according to claim 1, wherein, At least one of the following conditions must be met: (1) The effective viable count in the functional composite microbial system is greater than or equal to 1.0 × 10⁻⁶. 8 CFU / g; (2) The nitrogen-fixing bacteria are either Rhizobium or Nitrogenobacterium; (3) The phosphate-solubilizing bacteria are either Pseudomonas or Bacillus; (4) The lignocellulose-degrading bacteria are Trichoderma genus; (5) The arbuscular mycorrhizal fungus is of the genus Gynomycorrhizal, and the number of spores of the arbuscular mycorrhizal fungus is >30 / g; (6) The sulfur-oxidizing bacteria are multifunctional bacteria, and the effective viable count of the sulfur-oxidizing bacteria is greater than or equal to 1.0 × 10⁻⁶. 8 CFU / g.

6. The method according to claim 1 or 5, wherein, At least one of the following conditions must be met: (1) Based on the effective viable bacteria count, the ratio of lignocellulose-degrading bacteria: nitrogen-fixing bacteria: phosphate-solubilizing bacteria in the functional composite microbial system is 1:(0.1~10):(0.1~10), preferably 1:(0.5~5):(0.5~5); (2) The inoculation amount of the functional composite microbial system is 100~200 g / m³. 2 ; (3) The inoculation method of the functional composite microbial system is spraying with water suspension or mixing with dry carrier and spreading.

7. The method according to claim 1, wherein, The inoculation amount of the arbuscular mycorrhizal fungi is 100~200 g / m³. 2 The inoculation amount of the sulfur-oxidizing bacteria is 10~15 mL / m 2 .

8. The method according to claim 1, wherein, The stress-resistant fine-rooted plant is a grass, preferably one or more of foxtail grass, crabgrass, ryegrass or sorghum; The planting density of the stress-resistant fine-rooted plants transplanted into the primary soil-like substrate is 7-20 plants / m². 2 .

9. The method according to claim 1, wherein, The cultivation time for the primary soil-like substrate is 15 to 60 days, preferably 25 to 35 days; The seedling cultivation time for the stress-resistant fine-rooted plants is 20-40 days.

10. The method according to claim 1, wherein, The water management period is 1 to 2 growth cycles.

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