Movable tailings pond composite ecological restoration module and preparation method thereof

Abstract

The application discloses a movable tailing pond composite ecological restoration module and a preparation method thereof, and belongs to the technical field of mine ecological restoration. The module takes a tailing particle-containing substrate as the main body, and a prefabricated ecological restoration unit that can be transplanted as a whole is cultivated in a modular seedling container. The module surface is alternately arranged with a ground cover plant holding strip and a biological crust surface holding strip in the same direction. The former forms a root holding network by pressure planting of stem segments or creeping stem segments, and the latter inoculates algae, blue-green algae, moss fragments or a combination thereof on the surface of the bare substrate and covers the surface with a degradable macroporous mesh material. The bottom of the module is a bare particle substrate contact surface, which is directly attached to the original surface layer of the tailing pond to form a continuous substrate interface during transplantation. The application realizes the synergistic effect of plant root anchoring, crust surface layer consolidation and tailing substrate fusion through the alternate arrangement of the plant holding strip and the crust surface holding strip, and can significantly improve the surface layer stability of the tailing pond, the ground cover plant planting effect and the ecological restoration efficiency.

Description

Technical Field

[0001] This invention belongs to the field of mine ecological restoration technology, and particularly relates to a mobile tailings dam composite ecological restoration module and its preparation method. Background Technology

[0002] Metal tailings ponds are typical artificially degraded ecosystems formed during mining activities. Their accumulation not only occupies vast amounts of land resources, but the loose, exposed tailings surface is also highly susceptible to dust and erosion under wind and water forces, leading to the migration and spread of heavy metals and other pollutants, posing a serious threat to the surrounding soil, water bodies, and atmospheric environment. Tailings matrix typically exhibits characteristics such as low organic matter content, nutrient deficiency, loose particles, weak water retention capacity, and high heavy metal content, making vegetation establishment difficult, the surface prone to wind and water erosion, and potentially triggering heavy metal migration, dust pollution, and ecological risks. Therefore, how to quickly stabilize the tailings surface, promote vegetation establishment, and restore ecological functions is a key issue in the ecological restoration of tailings ponds.

[0003] Biological soil crusts (BSCs) are complex layered structures formed by the tight binding of cryptogams such as algae, cyanobacteria, mosses, and lichens with soil particles. Through microbial metabolic activity, they secrete extracellular polymers to cement loose surface particles into stable aggregates, thereby enhancing the surface's resistance to erosion. However, single-site biocrust remediation technology has significant limitations: after in-situ inoculation in tailings ponds, it typically takes several weeks to months for the crust to form a stable structure. During this process, the crust material is highly susceptible to adverse factors such as wind, runoff erosion, and strong sunlight. More importantly, although biocrusts possess a certain degree of erosion resistance, their structural strength is limited. In the event of extreme rainfall events, the underdeveloped crust is easily damaged by rainwater splash and surface runoff, leading to remediation failure. This has become one of the core bottlenecks restricting the widespread application of biocrust remediation technology.

[0004] Utilizing tolerant plants for vegetation restoration in tailings ponds is another important technical approach. Phytoremediation can enhance the stability of the tailings surface through root anchorage and reduce the migration risk of heavy metals through plant absorption and rhizosphere deposition. However, tailings substrates are characterized by extremely low organic matter content, severe nutrient deficiency, and significant heavy metal stress effects. Direct sowing or transplanting of plants results in very low establishment rates, and even when a few survive, they often grow poorly, making it difficult to form a sustainable and effective vegetation cover. The establishment barriers faced by phytoremediation alone in tailings pond environments significantly limit the remediation efficiency and applicability of this technology.

[0005] To address the limitations of the two aforementioned technologies, researchers have attempted to combine biocrust remediation with phytoremediation. This involves using the biocrust to improve the surface microenvironment and promote plant colonization, while simultaneously leveraging plant roots to enhance deep-layer retention. However, most existing technologies still rely on in-situ inoculation of biocrust material and plant seeds separately. The biocrust material lacks effective protection, and plants struggle to obtain sufficient nutrients during the initial stages of biocrust formation, failing to achieve true synergy between the two in both time and space. While some commercially available prefabricated straw mats or ecological mats are convenient for transportation and installation, their bottoms typically have a fiber isolation layer or dense substrate to maintain module shape and prevent substrate loss. This practice severely hinders the downward penetration of plant roots and the natural integration of the module substrate with the in-situ tailings layer, resulting in a layered interface between the remediation module and the underlying tailings, significantly reducing the long-term remediation effectiveness. More importantly, existing technologies are all based on in-situ construction or have the aforementioned isolation defects. There is a lack of modular products that can be prefabricated, transported, and quickly laid, and can be integrated with the original strata without interface. It is difficult to achieve the synergistic effect of crust "stabilizing the surface" and plant "stabilizing the roots", and cannot meet the needs of large-area and high-efficiency tailings dam ecological restoration.

[0006] To address the aforementioned technical problems, this invention provides a mobile tailings pond biocrust-ground cover plant composite ecological module and its preparation method. Summary of the Invention

[0007] The purpose of this invention is to provide a mobile tailings dam composite ecological restoration module and its preparation method, so as to solve the problems of difficult plant establishment, low survival rate of biological crust sowing, insufficient integration of ordinary ecological blankets with the in-situ matrix of tailings, and difficulty in standardizing the production of restoration products in the existing tailings dam ecological restoration process.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A mobile tailings dam composite ecological restoration module is a prefabricated ecological restoration unit that can be transplanted as a whole, cultivated from a tailings-containing granular substrate in a modular seedling container. The surface of the module is configured with alternating ground cover plant holding strips and biocrust surface-fixing strips, both extending in the same direction. The ground cover plant holding strips contain segmented stem segments or stolons of ground cover plants, which are embedded in the substrate and form a root holding network through rooting. The biocrust surface-fixing strips contain algae, cyanobacteria, moss fragments, or combinations thereof inoculated on the exposed granular substrate surface, and the surface of the strip is covered with a biodegradable macroporous mesh material. The bottom of the module is a contact surface formed by the direct exposure of the tailings-containing granular substrate, which is used to adhere to the in-situ surface of the tailings dam during transplantation to form a continuous substrate interface.

[0010] Furthermore, the tailings-containing granular matrix is ​​composed of a mixture of tailings and auxiliary materials, wherein the tailings constitute 30%–90% by mass. Preferably, the tailings-containing granular matrix comprises, by mass, 40–80 parts sand, loam, or garden soil, 10–50 parts tailings, 0.5–8 parts clay minerals, 0.5–10 parts organic amendment, and 0.1–3 parts water-retaining material. This matrix, with tailings as a major component, more closely resembles the physicochemical properties of the original tailings pond, facilitating rapid integration of the modular matrix with the original tailings layer after transplanting and reducing root penetration barriers caused by interface differences.

[0011] Furthermore, the width of the ground cover plant holding strip is 3–10 cm, and the width of the biological crust surface-fixing strip is 3–10 cm. The strip width can be adjusted according to the slope, erosion intensity, and plant growth characteristics of the target restoration area, but should be kept within the above range to ensure the synergistic effect of holding and consolidating.

[0012] Furthermore, the ground cover plants are those that are tolerant of poor soil, drought, and metal stress, and possess creeping growth characteristics or the ability to easily root from internodes. These plants can rapidly form a continuous root network by laying stem segments flat and pressing them in, maintaining a strong ability to establish and expand even in the harsh environment of tailings ponds.

[0013] Furthermore, the biodegradable macroporous mesh material only covers the surface of the biocrust-fixing strips, and no fiber isolation layer is provided at the bottom of the module. This design is a key feature that distinguishes it from traditional ecological blankets: the top mesh material is only used for temporary protection of the crust inoculation area and does not extend to the bottom surface of the module, thereby ensuring direct contact between the module substrate and the original tailings layer after transplanting, and free flow of water, nutrients, and roots.

[0014] Furthermore, the module has a thickness of 2–6 cm and a rectangular shape with sides ranging from 20 cm to 100 cm. This thickness range provides an optimal compromise between balancing root growth space and overall module transportability; if the module is too thin, the root anchorage will be insufficient, while if it is too thick, the transportation and installation difficulties will increase.

[0015] This invention also provides a method for preparing the above-mentioned mobile tailings dam composite ecological restoration module, comprising the following steps:

[0016] S1. Preparation of tailings-containing granular matrix: Mix the tailings with at least one auxiliary material selected from sand, clay minerals, organic amendments, and water-retaining materials, and add water to adjust to a suitable moisture content. This moisture content is usually suitable when it can be formed into a ball by hand and crumbles easily under light pressure. The specific value can be adjusted between 20% and 35% depending on the matrix composition.

[0017] S2. Constructing the substrate layer: Fill the modular seedling container with the substrate obtained in step S1 to form a substrate layer with a thickness of 1-5 cm. Lightly compact the substrate during filling to ensure that the substrate layer is uniform and dense, but do not over-compact it to avoid affecting aeration and root penetration.

[0018] S3. Define strip zones: Plan alternating ground cover plant planting zones and biocrust planting zones along the same direction on the surface of the substrate layer. The strip zones can be planned in a strip, patch, checkerboard, or grid pattern, with strips being preferred for standardized operation and large-scale production.

[0019] S4. Planting ground cover plants: Lay out segmented stems or stolons with nodes in the ground cover plant planting area, cover with soil, lightly press, and then retain moisture for cultivation. The stem segments are laid in strips, which is much more efficient than individual cuttings and is conducive to large-scale production.

[0020] S5. Inoculation Crust Material: Algae, cyanobacteria, moss fragments, or combinations thereof are inoculated within the biocrust colonization area, and a biodegradable macroporous mesh material is placed over the surface of this inoculation area. This macroporous mesh material is only placed over the top of the colonization area to provide moisture retention, shade, wind erosion resistance, and anchoring of the inoculated material; it is not placed at the bottom of the module.

[0021] S6. Co-cultivation: Under suitable conditions, co-cultivate for 20–60 days to allow ground cover plants to form a root network and crusting material to form an initial crust layer, thus obtaining a movable tailings dam composite ecological restoration module that can be removed as a whole. During the co-cultivation period, suitable temperature and humidity conditions must be maintained, and necessary irrigation and light management must be carried out.

[0022] Preferably, in step S5, at least one of the following is added simultaneously: an extracellular polymer, an extracellular polymer-producing microorganism, a nitrogen-fixing microorganism, a growth-promoting microorganism, or a natural cementing agent. These additives can accelerate the formation of the biocrust, improve the crust strength, and enhance the cementing effect on surface particles.

[0023] Preferably, the biodegradable macroporous mesh material is selected from at least one of jute mesh, coconut fiber mesh, straw fiber mesh, burlap, or biodegradable polymer mesh. Such natural fiber meshes can degrade naturally after a certain period, requiring no secondary recycling and causing no pollution to the remediation area.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention uses a substrate containing tailings particles as a common planting interface for biological crust and ground cover plants. The substrate components are highly compatible with the in-situ materials of the tailings pond, which is conducive to the rapid integration of the module substrate with the original stratum after transplanting and the downward penetration of plant roots. It overcomes the interface incompatibility problem existing in traditional topsoil covering or ordinary ecological blankets.

[0026] (2) The present invention adopts a surface structure in which ground cover plant holding strips and biological crust surface fixing strips are arranged alternately, which avoids the shading inhibition of crust growth by high-density plant cover. At the same time, the biological crust can improve the surface microenvironment of adjacent plant strips, realizing the spatiotemporal synergy of deep anchoring of plant roots and surface consolidation of crust.

[0027] (3) The present invention covers the surface of the biocrust solid strip with a biodegradable macroporous mesh material, which provides moisture retention, shade and wind erosion protection for the fragile crust inoculum, significantly improving the crust success rate; at the same time, the protective mesh only covers the top of the crust area and does not extend to the bottom of the module, ensuring unobstructed contact between the module and the original tailings after transplantation.

[0028] (4) No fiber isolation layer is deliberately set at the bottom of the module of the present invention. After transplanting, the module substrate directly adheres to the original surface of the tailings pond, forming a continuous channel for water, nutrients and roots. The module and the original stratum gradually merge into a whole, fundamentally solving the drawback of the traditional prefabricated repair products and the repair foundation being "two layers".

[0029] (5) This invention enables the centralized cultivation of stable quality restoration modules under controlled conditions through prefabricated production in seedling containers, realizing the factory-based and standardized manufacturing of ecological restoration products. The products can be taken out, transported and spliced ​​for installation as a whole, and are suitable for rapid ecological coverage and engineering applications of large-area tailings ponds. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This image depicts the development process of artificially induced biocrusts on tailings substrate. A: Image of crust appearance; B: Crust thickness; C: Chlorophyll a content.

[0032] Figure 2 This is a preliminary assessment diagram of the effect of biological soil crust on the establishment process of ground cover plants. In the diagram: a: ​​Comparison of the establishment status of ground cover plants in tailings substrate under different crust treatments; b: Changes in moisture content of tailings substrate with incubation time under different treatments; c: Changes in the survival rate of plant leaves with incubation time under different treatments.

[0033] Figure 3 This is a top view schematic diagram of the mobile tailings dam composite ecological restoration module of the present invention.

[0034] Figure 4This is a cross-sectional structural diagram of the mobile tailings dam composite ecological restoration module of the present invention. Detailed Implementation

[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0036] All raw materials used in this invention are not particularly limited in their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0037] There are no particular restrictions on the purity of any of the raw materials used in this invention. However, this invention preferably uses raw materials of analytical grade or purity commonly used in the field of chemical synthesis.

[0038] Example 1

[0039] (1) Preparation of tailings particle matrix

[0040] Weigh out 30 parts by weight of tailings sand, 50 parts by weight of sand, 3 parts by weight of bentonite, 5 parts by weight of well-rotted organic fertilizer, 3 parts by weight of biochar, and 0.5 parts by weight of polyacrylamide water-retaining agent from a copper tailings dam. Mix thoroughly and add water to adjust the moisture content to 25%–30% to obtain a tailings-containing granular matrix. The preparation of this matrix results in a tailings mass percentage of approximately 33%, which not only provides suitable physical structure and nutrient conditions for subsequent plant root growth and crust formation, but also closely resembles the physical properties of the original tailings, facilitating the integration of the transplanted modules with the original strata.

[0041] (2) Construction of modular matrix layer

[0042] The tailings-containing granular substrate obtained in step (1) is filled into a modular seedling tray (either rigid plastic or biodegradable) with internal dimensions of 100 cm × 50 cm × 6 cm, spread out and lightly compacted to form a uniform granular substrate layer with a thickness of 4 cm. This thickness ensures sufficient space for root growth and facilitates subsequent removal and transportation of the entire tray.

[0043] (3) Setting up plant planting area and bark-forming planting area

[0044] Along the length of the module, alternating strips of ground cover plant anchorage and biological crust surface stabilization are created on the matrix layer surface: five of each type of plant anchorage strip are 8 cm wide, and five of each type are 6 cm wide, forming an alternating strip distribution pattern. This design avoids the shading and inhibition of crust growth caused by high-density plant cover, while the presence of the crust strips also provides a surface microenvironment improvement function for adjacent plant strips.

[0045] (4) Planting of ground cover plants

[0046] Select *Phylacanescens*, a creeping plant that readily roots at its nodes and is tolerant of poor soil and metal stress. Cut robust stolons into segments (approximately 5–8 cm long) containing 2–3 nodes. Lay the stem segments flat along the plant's support strip, spacing them 5–8 cm apart, and gently press them into the substrate surface, ensuring the nodes are embedded about 1 cm below the substrate surface. Then cover with a thin layer of substrate about 0.5 cm thick, gently press, and spray with water to ensure close contact between the stem segments and the substrate. Keep the substrate moist and cultivate at 20–30°C. New roots will begin to sprout from the nodes after one week.

[0047] (5) Inoculation of biological crust

[0048] Nostoc sp. and Anabaena sp. were cultured in BG11 liquid medium at 25°C, under a light intensity of 3000 lux and a light-dark cycle of 12h:12h for 15 days, respectively, to obtain a density of approximately 10. 6 ~10 7 Algal solution was prepared at a concentration of cells / mL. Simultaneously, gametophytes of *Bryum sp.* were collected and shredded into small fragments of 1–2 mm. The algal solution and moss fragments were mixed thoroughly at a volume ratio of 3:1 and sprayed evenly onto the biocrust-forming zone. The spraying volume of algal solution was approximately 2 L / m³. 2 The amount of moss fragments used is approximately 150 g / m². 2 (Based on fresh weight). After spraying, the inoculum can be seen to adhere evenly to the surface of the granular matrix.

[0049] (6) Coverage protection

[0050] A biodegradable jute fiber net with a pore size of 1–2 cm is placed only above the bio-crust surface-fixing strip area. The edges of the net are pressed into the substrate on both sides for fixation, ensuring that the net adheres to the surface of the crust area, but does not extend to cover the plant-fixing strip area, and is not placed at the bottom of the module. This jute net serves to retain moisture, provide shade, reduce wind speed, and anchor the inoculum on the crust, significantly improving the initial survival rate and stability of the crust material. The entire bottom of the module remains an exposed granular substrate contact surface, without any fiber isolation layer or dense padding layer.

[0051] (7) Joint cultivation

[0052] Place the seedling trays that have undergone the above operations in a greenhouse or plastic tunnel for co-cultivation under conditions of 20-30℃ and natural light (supplemented with artificial light of 2000-4000 lux on cloudy days). Spray water 1-2 times daily to maintain the substrate moisture content between 25% and 35%, avoiding waterlogging. During the cultivation period, the stem segments in the plant strip zone will successively root and grow new stolons and leaves, while the algae and moss fragments in the crust strip zone will gradually proliferate, expand, and secrete extracellular polymers, binding the surface particles together.

[0053] After 20 days of cultivation, obvious blue-green algae coverage and particle aggregation were observed in the biocrust solidification zone; after 40 days of cultivation, the algae-moss crust had formed a continuous cover layer, and its appearance and adhesion were similar to those of naturally developed algal and moss crusts in tailings ponds. Measurements were taken from modular crust areas, and the crust thickness and chlorophyll a content were close to the levels of natural tailings pond crusts (see...). Figure 1 A, Figure 1 B and Figure 1 C).

[0054] Simultaneously, using the same method as the module preparation, BSC treatment groups (with crusting) and blank control groups (without crusting) were set up on the tailings matrix, and *Hylocereus undatus* stem segments were planted simultaneously. Plant survival and growth status were observed on days 10, 30, and 60 of cultivation. Results are as follows: Figure 2 As shown: the survival rate of ground cover plants in the BSC treatment group was significantly higher than that in the control group at 60 days, and the plants showed new branching and leaf growth. Figure 2 a); BSC coverage significantly increased the moisture content of the tailings matrix ( Figure 2 b), and maintained a high leaf survival rate throughout the entire culture period ( Figure 2 c). It can be seen that during the co-cultivation stage, the crusting strips in the module can effectively improve the microenvironment for plant establishment, while the gradual establishment of the plant root system further enhances the integrity of the module, and the two achieve synergistic effects.

[0055] (8) Overall transplanting and laying

[0056] After 40-60 days of co-cultivation, the modules are removed from the seedling trays as a whole. At this time, the bottom of the module is the exposed substrate containing tailings particles, the plant roots have already interwoven into a network at the bottom, and the crust strips are firmly fixed to the surface. The modules are transported to the tailings pond area to be remediated and laid directly on the in-situ tailings surface, ensuring close contact between the exposed substrate at the bottom of the module and the in-situ surface of the tailings pond. The modules can be spliced ​​together to form a continuous cover. After laying, light compaction is applied at 5-10 kPa, and water is sprayed immediately for 1-2 weeks for curing. After transplanting, the plant roots quickly penetrate downwards into the in-situ tailings layer, "stitching" the module and the in-situ layer together. The substrate interface at the bottom of the module gradually merges with the underlying tailings layer, forming a continuous integral substrate layer, overcoming the "two-layer skin" problem caused by the bottom isolation layer in traditional prefabricated ecological blankets.

[0057] Example 2

[0058] This embodiment, based on Example 1, increases the mass fraction of tailings sand in the tailings-containing particle matrix to 50 parts (while adjusting the sand to 30 parts, with the remaining components unchanged), making the tailings mass percentage approximately 56% to simulate a remediation scenario under high tailings content conditions. All other steps, parameters, and materials are the same as in Example 1. After 40 days of co-cultivation, the resulting module showed a crust coverage comparable to Example 1, with normal rooting and stolon expansion, but slightly lower plant height. After transplanting the module entirely to the original tailings pond, the bottom fusion effect was also good. Testing showed that after 30 minutes of wind tunnel erosion simulating a 10 m / s wind speed, the surface erosion of the module was only 7.2% of that of unprotected bare tailings (5.1% in Example 1), indicating that even with increased tailings content, the module still possesses excellent wind erosion resistance.

[0059] Example 3

[0060] This embodiment is based on Embodiment 1 with the following modifications:

[0061] (i) The ground cover plant was replaced by Cynodon dactylon stolons, which are easy to root at the nodes and are drought- and barren-tolerant;

[0062] (ii) In the biocrust inoculation step, in addition to the algae solution and moss fragments, xanthan gum was added simultaneously as a natural cementing agent at a spray concentration of 0.5 g / L, and nitrogen-fixing bacteria (Azotobacter sp.) solution (10 g / L) was also added. 7 CFU / mL, dosage 200 mL / m 2 To improve nitrogen nutrition in tailings;

[0063] (iii) The covering material was changed to coconut fiber mesh with a pore size of 1 cm.

[0064] After 35 days of co-cultivation, the plant coverage of the module reached over 85%, and the chlorophyll a content in the crust increased by approximately 22% compared to Example 1. Following transplanting, a simulated rainfall test (80 mm / h rainfall intensity, lasting 20 minutes) was conducted to demonstrate resistance to water erosion. No significant grooving was observed on the module surface, and the runoff sediment content was only 8.3% of that of bare tailings without the module, exhibiting outstanding resistance to water erosion. This example demonstrates that the module has broad plant species adaptability and scalability of functional components.

[0065] Example 4

[0066] This embodiment changes the strip width and matrix layer thickness: plant holding strips with a width of 5cm and biological crust surface holding strips with a width of 5cm are alternately arranged along the length of the module; the matrix thickness is 5cm. Other operations are the same as in Embodiment 1.

[0067] The narrower strips further promoted the interpenetration between the crust and the plants. After 45 days of co-cultivation, the crust almost covered all the crust strip areas and partially spread into the gaps between the plant strips. The plant stolons also crossed the crust strips to take root, forming an interwoven and consolidated network. The overall tensile strength of the module was increased by about 15% compared to Example 1, making it suitable for tailings dam slope restoration with a large slope.

[0068] Comparative Example 1: Module with an isolation layer at the bottom

[0069] The preparation method for this comparative example is the same as that for Example 1, the only difference being that before filling the substrate in step (2), a layer of 80 g / m³ is laid at the bottom of the seedling tray. 2 The non-woven fabric serves as an isolation layer, completely covering the bottom of the module.

[0070] When the prepared modules were transplanted to the surface of the tailings dam, most of the plant roots were coiled inside the modules due to the barrier of the non-woven fabric, with only a few fine roots emerging from the gaps in the non-woven fabric. The module matrix and the original tailings layer failed to form a continuous interface.

[0071] Sixty days after transplanting, the module was uncovered for observation. It was found that most of the bottom area was dry and loose, the module was separated from the original soil layer, and the wind erosion resistance was significantly reduced compared with Example 1 (the wind erosion was 3.5 times that of Example 1). The plant also showed signs of premature aging in the later stage of growth.

[0072] Comparative Example 2

[0073] This comparative example omits the alternating strip design, instead using the entire module surface as a plant planting area, fully inoculating it with bio-crust material, and covering the entire surface with jute netting. All other parameters are the same as in Example 1.

[0074] During the co-cultivation period, the ground cover plants rapidly spread and formed a high-density cover layer, resulting in the underlying crust material being in a low-light, high-humidity environment for an extended period. This severely inhibited the growth of cyanobacteria and mosses. After 40 days of cultivation, the crust coverage rate was less than 15%, mainly concentrated in the sparsely covered peripheral areas. Furthermore, the plant roots lacked the crust to consolidate the surface substrate, making some areas susceptible to slight water erosion during watering. After transplanting, the module's resistance to water erosion was significantly weaker than in Example 1, with runoff sediment volume approximately 2.8 times higher. This indicates that the lack of alternating distribution of the cover disrupted the synergistic relationship between the crust and the plants.

[0075] Comparative Example 3

[0076] In this comparative example, in step (6) of Example 1, no protective netting was used to cover the biological crust fixation strip, and the crust inoculum was directly exposed to the air.

[0077] During the co-cultivation period, due to rapid water evaporation, excessive sunlight, and wind disturbance, some of the inoculated algae and moss fragments dried and died, while others were blown out of the strip area. By 40 days of cultivation, the crust coverage rate was only 31%, and the crust was loose and fragile. During subsequent transplanting, the crust strips were further broken and lost during transportation and laying, making it difficult to play a surface consolidation role.

[0078] Comparative Example 4

[0079] This comparative example simulates the traditional in-situ construction and remediation method. Strips of the same specifications as in Example 1 were directly divided in situ on the surface of the tailings dam. Stem segments of *Hymenochloa chinensis* were planted in each strip, and a mixed algae-moss inoculum was sprayed on top. The crusted area was then covered with jute netting. However, no modules were pre-fabricated, and no pre-cultivation of a tailings particle matrix was performed.

[0080] Under natural conditions, due to the extremely poor nutrient content and water retention of the tailings matrix, plant stem segments developed roots slowly and had a high mortality rate. The inoculated biocrust material also lacked a stable, moist protective environment in the early stages, resulting in slow crust formation and significant susceptibility to wind and rain. After 60 days, the plant survival rate was only 28% of that in Example 1, the crust coverage was less than 20%, and surface wind erosion remained severe. This indicates that the prefabricated modular strategy of this invention significantly improves remediation efficiency and success rate by providing an optimized matrix environment and concentrated initial maintenance.

[0081] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A mobile tailings dam composite ecological restoration module, characterized in that, It is a prefabricated ecological restoration unit that can be transplanted as a whole, cultivated in a modular seedling container with a tailings granular substrate. The surface of the module is configured with alternating strips of ground cover plant holding and strips of biological crust surface holding, both extending in the same direction; The ground cover plant holding strip includes segmented stem segments or creeping stem segments of ground cover plants, which are embedded in the substrate and form a root holding network through rooting; The biocrust surface-fixing strip contains algae, cyanobacteria, moss fragments or combinations thereof inoculated on the surface of the bare granular matrix, and the surface of the strip is covered with a biodegradable macroporous mesh material. The bottom of the module is a contact surface formed by directly exposing the tailings particle matrix, which is used to adhere to the original surface of the tailings dam during transplantation to form a continuous matrix interface.

2. The mobile tailings dam composite ecological restoration module according to claim 1, characterized in that, The tailings-containing particle matrix is ​​composed of a mixture of tailings and auxiliary materials, wherein the mass percentage of tailings is 30% to 90%.

3. The mobile tailings dam composite ecological restoration module according to claim 2, characterized in that, The tailings-containing particle matrix comprises, by mass, 40-80 parts of sand, loam or garden soil, 10-50 parts of tailings, 0.5-8 parts of clay minerals, 0.5-10 parts of organic amendment, and 0.1-3 parts of water-retaining material.

4. The mobile tailings dam composite ecological restoration module according to claim 1, characterized in that, The width of the ground cover plant holding strip is 3–10 cm, and the width of the biological crust holding strip is 3–10 cm.

5. The mobile tailings dam composite ecological restoration module according to claim 1, characterized in that, The ground cover plants are those that are tolerant of poor soil, drought, and metal stress, and have creeping growth characteristics or easy rooting characteristics at the nodes.

6. The mobile tailings dam composite ecological restoration module according to claim 1, characterized in that, The biodegradable macroporous mesh material only covers the surface of the biocrust surface-fixing strip, and no fiber isolation layer is provided at the bottom of the module.

7. The mobile tailings dam composite ecological restoration module according to any one of claims 1 to 6, characterized in that, The module has a thickness of 2 to 6 cm and a rectangular shape with a side length of 20 cm to 100 cm.

8. A method for preparing a mobile tailings dam composite ecological restoration module, characterized in that, Includes the following steps: S1. Preparation of tailings granular matrix: Mix tailings with at least one auxiliary material selected from sand, clay minerals, organic amendments, and water-retaining materials, and add water to adjust to a suitable moisture content; S2. Constructing the substrate layer: Fill the modular seedling container with the substrate obtained in step S1 to form a substrate layer with a thickness of 1 to 5 cm; S3. Define strip zones: Plan alternating ground cover plant planting zones and biological crust planting zones along the same direction on the surface of the matrix layer; S4. Planting ground cover plants: Lay out segments of stem with nodes or stolons in the planting area of ​​ground cover plants, cover with soil and lightly press down, and then keep moist for cultivation; S5. Inoculation crust material: Inoculate algae, cyanobacteria, moss fragments or combinations thereof in the biological crust colonization area, and cover the surface of the inoculation area with a biodegradable macroporous mesh material; S6. Co-cultivation: Under suitable conditions, co-cultivate for 20 to 60 days to allow ground cover plants to form a root network and crust material to form an initial crust layer, thus obtaining a mobile tailings dam composite ecological restoration module that can be removed as a whole.

9. The preparation method according to claim 8, characterized in that, In step S5, at least one of the following is also added simultaneously: an extracellular polymer, an extracellular polymer-producing microorganism, a nitrogen-fixing microorganism, a growth-promoting microorganism, or a natural binder.

10. The preparation method according to claim 8, characterized in that, The biodegradable macroporous mesh material is selected from at least one of jute mesh, coconut fiber mesh, straw fiber mesh, burlap, or biodegradable polymer mesh.

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