Ecological restoration method for open pit coal mine dumping site

Abstract

The invention discloses an ecological restoration method for an open pit coal mine waste dump, and belongs to the technical field of ecological restoration of mining areas. The remediation method comprises the steps that the slopes of the waste dump are subjected to stage treatment, and a platform is arranged between every two stages of slopes; an annular water collecting ditch is formed in the lowermost portion of the whole waste dump; s2, a soil conditioner is applied to the platform area and the side slope, deep ploughing is conducted, and soil covering is conducted; s3, selecting seedlings of hippophae rhamnoides, pinus tabulaeformis and caragana microphylla and seeds of Astragalus adsurgens, and soaking roots of the seedlings of hippophae rhamnoides, pinus tabulaeformis and caragana microphylla in a mixed bacteria solution composed of arbuscular mycorrhizal fungi and trichoderma; s4, hippophae rhamnoides and adsura adsura are planted on the side slope in a mixed mode, and Chinese pine, caragana microphylla and adsura adsura are planted in the platform area in a mixed mode. The remediation method provided by the invention has the advantages that the problems of soil structure damage, low fertility and the like caused by mining of the dumping site can be effectively improved, the soil stability is enhanced, the vegetation coverage rate is increased, and then the ecological environment is gradually remedied.

Description

Technical Field

[0001] The present application belongs to the technical field of ecological restoration of mining areas, and in particular, relates to an ecological restoration method for an open-pit coal mine dump. Background Art

[0002] With the advancement of open-pit coal mining, the ecological problems of spoil dumps have become increasingly prominent. Most of the soil comes from the topsoil of the non-cultivated layer, showing the characteristics of being unripe and with excessive heavy metal content. During the mining process, large-scale machinery frequently operates, and the disorderly stacking and long-term backlog of earthwork have caused a devastating blow to the nutritional structure of the soil in the spoil dump. The organic matter, nitrogen, phosphorus, potassium and various trace elements necessary for plant growth are extremely scarce, the soil structure is fragmented, the ability to retain water and fertilizer is almost lost, the bulk density is abnormally high, the cohesion is weak, and wind erosion occurs frequently. At the same time, the microbial community and enzyme system in the soil are almost collapsed, the channels for material circulation and energy conversion are completely cut off, and the soil fertility and physical and chemical properties are in a desperate situation. Such harsh soil conditions make it difficult for vegetation to take root, and the ecological balance is ruthlessly broken. Summary of the invention

[0003] In view of this, the present application provides an ecological restoration method for an open-pit coal mine dump, which ingeniously creates a suitable site basic environment by grading the slopes and carefully constructing platforms and circular drainage ditches; accurately mixes and applies special soil conditioners, cooperates with deep plowing and covering operations, and deeply improves the soil texture; carefully selects sea buckthorn, Chinese pine, Caragana seedlings and Astragalus seeds, and after soaking in a special mixed bacterial solution, mixes them in the slope and platform area according to a scientific and reasonable proportion; strictly implements a regular irrigation system in the early stage of planting, and continuously carries out all-round monitoring and flexible maintenance measures in the later stage. This series of interlocking, innovative and systematic steps aims to fully restore the physical structure and fertility level of the soil, successfully rebuild the vegetation community, and finally achieve the comprehensive ecological restoration of the open-pit coal mine dump, effectively reverse the ecological imbalance caused by mining activities, steadily promote the dump ecosystem to a stable and healthy road, greatly reduce the adverse impact on the surrounding ecological environment, and significantly improve the overall ecological benefits and environmental quality.

[0004] In a first aspect, the present application provides an ecological restoration method for an open-pit coal mine dump, the restoration method comprising the following steps: S1. The slopes of the dump are graded, and platforms are set between the slopes of each level, and the platforms are compacted; a circular drainage ditch is set at the bottom of the entire dump to collect excess water seeping from the dump and drain it to the treatment pool; S2. Apply soil conditioner to the platform area and slope, deep plow and cover the soil; S3. Select seedlings of seabuckthorn, Chinese pine, Caragana korshinskii and seeds of Astragalus membranaceus, and soak the roots of the seedlings of seabuckthorn, Chinese pine and Caragana korshinskii in a mixed bacterial solution composed of arbuscular mycorrhizal fungi and Trichoderma for 12-18 hours. The volume ratio of arbuscular mycorrhizal fungi to Trichoderma in the mixed bacterial solution is 2-4:1, and the spore concentration of both fungi is 5×10 7 - 3×10 8 cfu / mL; S4. Plant seabuckthorn and Astragalus astragali in a ratio of 3-5:1-2 on the slope, and plant Pinus tabulaeformis, Caragana microphylla and Astragalus astragali in a ratio of 1-3:2-4:1-2 on the platform area; S5. In the first three months after planting, irrigation should be carried out every half a month, with each irrigation volume of 20-30 cubic meters per hectare. After that, the irrigation frequency and water volume should be adjusted appropriately according to the precipitation conditions. S6. Regularly monitor the growth of vegetation and adjust maintenance measures in a timely manner based on the monitoring results.

[0005] By adopting the above technical scheme, the present application firstly grades the slope in step S1 and sets up a platform and a circular drainage ditch, which solves the problem of soil loss and soil erosion caused by the terrain and poor drainage in the dumping site, and stabilizes the site environment. Step S2 applies a soil conditioner composed of blast furnace slag, rice husk charcoal, chicken manure organic fertilizer, peat soil, potassium sulfate and a specific composite bacterial agent and deep plows and covers the soil. Blast furnace slag improves soil structure, rice husk charcoal improves water and fertilizer retention, chicken manure organic fertilizer provides rich nutrients, peat soil enhances fertility and water retention, potassium sulfate supplements potassium, and composite bacterial agents optimize soil microecology, thereby effectively improving the physical and chemical properties of the soil, improving soil fertility, and laying a good foundation for vegetation growth. Step S3 soaks the roots of sea buckthorn, Chinese pine, and Caragana seedlings in a specific mixed bacterial solution to enhance the symbiotic relationship between the seedling roots and beneficial fungi, and improve their adaptability and nutrient absorption capabilities in harsh soil environments. In step S4, specific plants are planted in a mixed manner on the slope and platform areas according to specific proportions, and the ecological characteristics of different plants are utilized, such as the windbreak and soil fixation of sea buckthorn and Pinus tabulaeformis, the soil improvement of Caragana microphylla, and the rapid coverage and nitrogen fixation of Astragalus membranaceus, to promote the stable construction of vegetation communities. In step S5, regular irrigation in the early stage ensures the water demand of the initial growth of plants, and regular monitoring and timely maintenance measures in step S6 can be dynamically adjusted according to vegetation growth and soil changes to ensure the effectiveness and sustainability of the entire ecological restoration process. Through this series of steps, the problems of poor soil structure, low fertility, and difficulty in vegetation growth in the open-pit coal mine dump were successfully solved, the physical structure and fertility of the soil were restored, a stable vegetation community was rebuilt, the ecological imbalance caused by mining was effectively improved, and the dump ecosystem was promoted to develop in a stable and healthy direction, reducing the negative impact on the surrounding environment and improving the overall ecological benefits.

[0006] Optionally, in step S2, the soil conditioner is composed of the following components in parts by weight: 40-80 parts of blast furnace slag, 20-40 parts of rice husk charcoal, 15-30 parts of chicken manure organic fertilizer, 10-20 parts of peat soil, 3-8 parts of potassium sulfate, and 0.3-0.8 parts of composite bacterial agent; The composite bacterial agent consists of Bacillus licheniformis, photosynthetic bacteria and lactic acid bacteria in a mass ratio of 2-4:1-3:1-3.

[0007] By adopting the above technical scheme, the blast furnace slag in the soil conditioner can play a key role in improving the soil structure with its unique physical structure characteristics, effectively increase the porosity of the soil, enhance the air permeability and water permeability of the soil, expand the space for the growth of plant roots and promote gas exchange and water penetration. Rice husk charcoal, with its excellent adsorption performance and rich pore structure, significantly improves the soil's ability to retain water and fertilizer, reduces nutrient loss and stores more water for the soil to cope with the relatively dry and nutrient-deficient conditions of open-pit coal mine dumps. Chicken manure organic fertilizer is rich in a variety of nutrients necessary for plant growth, such as nitrogen, phosphorus, potassium and rich organic matter, which can supplement a large amount of nutrients to the soil, promote the rapid improvement of soil fertility, and meet the urgent needs of vegetation for nutrients in the early stages of growth. Peat soil can further enhance the fertility and water retention of the soil, and the humus and other ingredients it contains can improve the physical and chemical properties of the soil, making the soil more suitable for plant growth. Potassium sulfate accurately supplements the lack of potassium in the soil. Potassium plays an extremely important role in the photosynthesis, stress resistance and other physiological processes of plants, and helps plants grow healthily. The composite bacterial agent composed of a specific mass ratio of Bacillus licheniformis, photosynthetic bacteria and lactic acid bacteria can actively participate in the material cycle and energy conversion process of the soil. Bacillus licheniformis can decompose organic matter in the soil and release nutrients; photosynthetic bacteria can use light energy to synthesize organic matter and improve the soil microenvironment; lactic acid bacteria regulate the pH of the soil and inhibit the growth of harmful microorganisms, jointly optimize the soil microecological system, promote the establishment and prosperity of beneficial microbial communities in the soil, and create a good rhizosphere environment for plant growth, thereby comprehensively and multi-levelly improving the soil conditions of the open-pit coal mine dump, laying a solid foundation for the successful planting of subsequent vegetation and the smooth progress of ecological restoration projects, improving the effectiveness and reliability of the entire ecological restoration plan, and promoting the gradual restoration of vitality and balance of the dump ecosystem.

[0008] Optionally, in step S4, the planting spacing of seabuckthorn is 1.8-2.2 meters, the planting spacing of Pinus tabulaeformis is 3-4 meters, the planting spacing of Caragana microphylla is 1.2-1.8 meters, and the planting spacing of Astragalus adoxaceae is 0.3-0.6 meters.

[0009] Optionally, an impermeable geotextile is laid on the inner wall of the annular drainage ditch in step S1 to prevent water from seeping in and causing surrounding soil to collapse.

[0010] By adopting the above technical solution, this application can effectively prevent the water collected in the water collection ditch from infiltrating into the surrounding soil by laying an impermeable geotextile on the inner wall of the annular water collection ditch. The soil around the open-pit coal mine dump has poor structural stability due to the long-term impact of mining activities. Once a large amount of water infiltrates, it is very easy to cause the surrounding soil to collapse, resulting in further damage to the soil structure, affecting the overall stability and safety of the site, and may also cause many obstacles to subsequent ecological restoration projects, such as affecting the stability of plant planting pits and destroying the laid soil improvement layer. The laying of the impermeable geotextile is like building a reliable barrier for the water collection ditch, which firmly restricts the water in the water collection ditch and guides it to flow smoothly to the treatment pool, thereby maintaining the relative stability of the surrounding soil structure, ensuring the orderly advancement of the ecological restoration operation of the entire dump, and creating a good and safe basic environment for subsequent links such as soil improvement and plant planting, which is conducive to improving the success rate and durability of the entire ecological restoration project, and promoting the gradual restoration of balance and stability of the ecosystem of the open-pit coal mine dump.

[0011] Optionally, before planting sea buckthorn, Chinese pine and Caragana korshinskii in step S4, a layer of water retaining agent with a thickness of 3-5 cm is laid at the bottom of the planting pit.

[0012] By adopting the above technical solution, in view of the poor water and fertilizer retention of the soil in the open-pit coal mine dump, the laying of water retaining agent can significantly improve the water retention capacity of the soil in the planting pit. In the natural environment, especially in periods of scarce or uneven rainfall, the water retaining agent can quickly absorb and store a large amount of water. When the soil moisture content decreases, it can slowly release the stored water, providing a continuous and stable water supply for the roots of plants such as sea buckthorn, Chinese pine, and Caragana, effectively alleviating the stress caused by insufficient soil moisture on plant growth. This helps to improve the survival rate of plants, promote better development and growth of their roots, and enhance the adaptability of plants under adverse soil conditions, thereby promoting the construction and stable development of the entire vegetation community, laying a solid foundation for the ecological restoration of the open-pit coal mine dump, accelerating the restoration of the ecosystem, and improving the overall effectiveness and quality of ecological restoration.

[0013] Optionally, the water retaining agent comprises the following components by weight: 40-60 parts of cross-linked polyacrylamide; 20-30 parts of starch graft copolymer; and 10-20 parts of bentonite nanoparticles.

[0014] By adopting the above technical solutions, cross-linked polyacrylamide exhibits excellent water absorption and water retention properties with its unique three-dimensional network structure, absorbs and firmly locks water in large quantities, forms a stable water reserve, and effectively alleviates the dilemma of easy loss of soil water in open-pit coal mine dumps. Starch graft copolymers combine the biodegradability of starch bases with the high water absorption of synthetic polymers. In the process of strengthening soil water retention efficiency, they gradually degrade and transform into organic matter over time, which not only avoids long-term negative effects on the soil, but also continuously supplies organic carbon sources for soil microorganisms, nourishes and activates the soil micro-ecosystem, and creates a healthy and active rhizosphere environment for plant roots. Bentonite nanoparticles are cleverly embedded in the molecular gaps of cross-linked polyacrylamide and starch graft copolymers, expanding more abundant and diverse water absorption pathways and expansion space, significantly improving the overall water retention effect; at the same time, its special nanoscale structure enables it to fit tightly with soil particles, greatly enhancing the stability and uniformity of the water retainer in the soil matrix, effectively resisting the displacement and loss risks caused by rain erosion and physical changes in the soil, and ensuring the continuity and stability of the water retention effect. These three components complement each other and enhance their effectiveness synergistically, comprehensively and continuously optimizing the water retention capacity of the soil in the open-pit coal mine spoil dump, and carefully constructing a moist and stable soil moisture environment suitable for vegetation to take root and grow. This provides a solid and reliable guarantee and strong support for the steady progress and ultimate success of the ecological restoration project, effectively promotes the gradual recovery and prosperity of vegetation communities, and achieves the key leap from damage to restoration and reconstruction of the open-pit coal mine spoil dump ecosystem, promoting the comprehensive restoration of ecological balance and sustainable development.

[0015] Optionally, the preparation method of the cross-linked polyacrylamide is as follows: dissolving acrylamide monomer in deionized water to prepare a solution with a mass concentration of 20%-30%, adding a cross-linking agent N,N'-methylenebisacrylamide under nitrogen protection, wherein the amount thereof is 0.05%-0.1% of the mass of the acrylamide monomer, and simultaneously adding an initiator ammonium persulfate and an accelerator tetramethylethylenediamine to initiate a polymerization reaction, wherein the reaction temperature is controlled at 30-40°C, the reaction time is 2-4 hours, and after the reaction is completed, washing is performed to remove impurities and drying is performed to obtain the cross-linked polyacrylamide.

[0016] By adopting the above technical scheme, nitrogen protection can effectively prevent oxygen from interfering with the polymerization reaction, ensure the smooth progress of the reaction and improve the stability and purity of the product. The specific amount of cross-linking agent helps to build a three-dimensional network structure of appropriate density, so that the cross-linked polyacrylamide has good water absorption performance while maintaining good mechanical strength and stability, avoiding excessive cross-linking leading to a decrease in water absorption performance or a structure that is too tight to affect water entry. The appropriate combination of initiator and promoter and the precisely controlled reaction temperature and time can accurately regulate the rate and progress of the polymerization reaction, so that the reaction proceeds smoothly and orderly, thereby obtaining a cross-linked polyacrylamide product with a relatively uniform molecular weight distribution and stable performance. When the cross-linked polyacrylamide prepared in this way is applied to the water-retaining agent of the open-pit coal mine dump, it can efficiently exert its water absorption and water retention effects, stably store a large amount of water and slowly release it, effectively improve the moisture condition of the soil, and provide reliable water guarantee for vegetation growth, which greatly improves the effectiveness and reliability of the soil water retention link in the ecological restoration process of the open-pit coal mine dump, and promotes the efficient implementation and successful achievement of the entire ecological restoration project.

[0017] Optionally, the preparation method of the starch graft copolymer is as follows: starch is dispersed in deionized water to prepare a starch emulsion with a mass concentration of 10% - 15%, acrylic acid monomer is added under stirring, and its amount is 1-2 times the mass of starch, and then initiator potassium persulfate is added, and its amount is 0.5% - 1% of the mass of acrylic acid monomer. Graft copolymerization reaction is carried out at 60-70°C for 3-5 hours. After the reaction is completed, cooling, adjusting the pH value to 7-8, and then precipitating with ethanol, filtering, and drying to obtain the starch graft copolymer.

[0018] By adopting the above technical scheme, when preparing starch graft copolymer, the starch emulsion of specific mass concentration ensures the uniformity and stability of the reaction system, providing an ideal starting state for subsequent reactions. The precise amount of acrylic acid monomer enables it to fully combine with starch molecules, and the introduction of a large number of hydrophilic segments greatly enhances the water absorption efficiency of the copolymer, effectively making up for the lack of water retention capacity of the soil in the open-pit coal mine dump. The appropriate amount of initiator and the precise control of reaction temperature and time ensure the efficient and orderly advancement of the graft copolymerization reaction, thereby obtaining a product with stable structure and excellent performance. Cooling and pH adjustment after the reaction further stabilize the copolymer structure and reduce interference from side reactions. The starch graft copolymer after ethanol precipitation, filtration and drying plays a key role in the water retaining agent system. Its high water absorption continuously improves the water holding capacity of the soil and meets the water demand of plant growth; its biodegradability is gradually converted into organic nutrients in the long-term process, nourishing the soil microbial community, optimizing the soil microecological environment, and enhancing the activity and fertility of the soil. It works synergistically with cross-linked polyacrylamide and bentonite nanoparticles to build an efficient water-retention network, comprehensively improving the moisture conditions and physical and chemical properties of the soil, rebuilding a solid foundation for vegetation in open-pit coal mine spoil dumps, and effectively promoting the close connection and synergy of various links in ecological restoration projects from soil improvement to vegetation restoration, ultimately achieving comprehensive restoration and sustainable development of the ecosystem.

[0019] Optionally, the preparation method of the bentonite nanoparticles is as follows: the bentonite ore is crushed and passed through a 200-mesh sieve, the sieve material is dispersed in deionized water to prepare a suspension with a mass concentration of 5%-10%, and sodium hexametaphosphate as a dispersant is added under stirring in an amount of 0.5%-1% of the mass of the bentonite, and then ball milling is performed in a ball mill with a ball-to-material ratio of 5:1-10:1 and a ball milling time of 4-6 hours. After the ball milling is completed, the product is centrifuged, the precipitate is collected, and it is repeatedly washed with deionized water to remove impurities and dried to obtain the bentonite nanoparticles.

[0020] By adopting the above technical scheme, when the bentonite nanoparticles prepared by the above method are used in water retaining agents, with their nano-size advantage, on the one hand, they can be accurately filled in the molecular gaps of other water retaining agent components such as cross-linked polyacrylamide and starch graft copolymer, effectively expanding the water absorption channels and storage space inside the water retaining agent, significantly enhancing the water retention capacity of the entire water retaining agent, and better coping with the problem of poor water retention performance of soil in open-pit coal mine dumps; on the other hand, its nanostructure enables it to have a stronger binding force with soil particles, and can exist more stably in the soil environment. Even if it encounters rain erosion or physical disturbance of the soil, it is not easy to be lost from the soil, and it continuously and stably plays a role in improving soil structure and enhancing water retention performance, and then cooperates with other water retaining agent components to create good water retention conditions for the soil in the open-pit coal mine dump, and help vegetation growth and the smooth development and effective promotion of the entire ecological restoration project.

[0021] Optionally, the modified water-retaining agent is prepared by mixing cross-linked polyacrylamide and starch graft copolymer evenly, adding bentonite nanoparticles, and stirring at a speed of 200-300 rpm for 15-30 minutes to obtain the modified water-retaining agent.

[0022] Optionally, in step S2, the application amount of the soil conditioner is 1000 - 1300 kg / hm².

[0023] Optionally, in step S1.1, the height of each level of the slope is controlled at 3-5 meters, and the width of the platform between each level of the slope is 1-2 meters; the platform is compacted by a heavy roller, and the compaction degree is not less than 90%; the depth of the annular drainage ditch is 1-1.5 meters, the width is 0.8-1.2 meters, the slope of the annular drainage ditch is set to 0.5%-1%, and the treatment pool is equipped with water purification equipment.

[0024] In summary, the present invention includes at least one of the following beneficial technical effects.

[0025] This application aims to systematically repair the problems of poor soil structure, low fertility, and difficulty in vegetation growth in open-pit coal mine dumps through multiple steps: S1 Slope and site treatment to improve topography and drainage and stabilize the environment; S2 Spray special improvers to optimize soil physical and chemical properties and fertility with the help of the characteristics of each component; S3 Soak seedlings in bacterial solution to strengthen root symbiosis and adaptive absorption capacity; S4 Plant specific plants in a mixed manner in proportion to give full play to their ecological characteristics to build vegetation communities; S5 Early regular irrigation to retain water; S6 Regular monitoring and maintenance to adjust dynamically. Ultimately, the soil structure and fertility were successfully restored, the stable vegetation community was rebuilt, the ecological imbalance was improved, the healthy development of the dump ecosystem was promoted, the negative environmental impact was reduced, and the overall ecological benefits were improved.

[0026] This application can effectively prevent the water collected in the water collection ditch from seeping into the surrounding soil by laying an impermeable geotextile on the inner wall of the circular water collection ditch. The soil around the open-pit coal mine dump has poor structural stability due to the long-term impact of mining activities. Once a large amount of water seeps, it is very easy to cause the surrounding soil to collapse, resulting in further damage to the soil structure, affecting the overall stability and safety of the site, and may also cause many obstacles to subsequent ecological restoration projects, such as affecting the stability of plant planting pits and destroying the laid soil improvement layer. The laying of the impermeable geotextile is like building a reliable barrier for the water collection ditch, which firmly restricts the water in the water collection ditch and guides it to flow smoothly to the treatment pool, thereby maintaining the relative stability of the surrounding soil structure, ensuring the orderly advancement of the ecological restoration operation of the entire dump, and creating a good and safe basic environment for subsequent links such as soil improvement and plant planting, which is conducive to improving the success rate and durability of the entire ecological restoration project, and promoting the gradual restoration of balance and stability of the ecosystem of the open-pit coal mine dump.

[0027] 3. Cross-linked polyacrylamide exhibits excellent water absorption and water retention properties with its unique three-dimensional network structure. It absorbs and firmly locks water in large quantities, forming a stable water reserve, which effectively alleviates the dilemma of easy loss of soil water in open-pit coal mine dumps. Starch graft copolymers combine the biodegradability of starch bases with the high water absorption of synthetic polymers. In the process of strengthening soil water retention efficiency, they gradually degrade and transform into organic matter over time, which not only avoids long-term negative effects on the soil, but also continuously supplies organic carbon sources for soil microorganisms, nourishes and activates the soil micro-ecosystem, and creates a healthy and active rhizosphere environment for plant roots. Bentonite nanoparticles are cleverly embedded in the molecular gaps of cross-linked polyacrylamide and starch graft copolymers, expanding more abundant and diverse water absorption pathways and expansion space, significantly improving the overall water retention effect; at the same time, its special nanoscale structure enables it to fit tightly with soil particles, greatly enhancing the stability and uniformity of the water retainer in the soil matrix, effectively resisting the displacement and loss risks caused by rain erosion and soil physical changes, and ensuring the continuity and stability of the water retention effect. These three components complement each other and enhance their effectiveness synergistically, comprehensively and continuously optimizing the water retention capacity of the soil in the open-pit coal mine spoil dump, and carefully constructing a moist and stable soil moisture environment suitable for vegetation to take root and grow. This provides a solid and reliable guarantee and strong support for the steady progress and ultimate success of the ecological restoration project, effectively promotes the gradual recovery and prosperity of vegetation communities, and achieves the key leap from damage to restoration and reconstruction of the open-pit coal mine spoil dump ecosystem, promoting the comprehensive restoration of ecological balance and sustainable development. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present application more clear, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0029] With the advancement of open-pit coal mining, the ecological problems of spoil dumps have become increasingly prominent. Most of the soil comes from the topsoil of the non-cultivated layer, showing the characteristics of being unripe and with excessive heavy metal content. During the mining process, large-scale machinery frequently operates, and the disorderly stacking and long-term backlog of earthwork have caused a devastating blow to the nutritional structure of the soil in the spoil dump. The organic matter, nitrogen, phosphorus, potassium and various trace elements necessary for plant growth are extremely scarce, the soil structure is fragmented, the ability to retain water and fertilizer is almost lost, the bulk density is abnormally high, the cohesion is weak, and wind erosion occurs frequently. At the same time, the microbial community and enzyme system in the soil are almost collapsed, the channels for material circulation and energy conversion are completely cut off, and the soil fertility and physical and chemical properties are in a desperate situation. Such harsh soil conditions make it difficult for vegetation to take root, and the ecological balance is ruthlessly broken.

[0030] In view of this, the present application provides an ecological restoration method for an open-pit coal mine dump, which ingeniously creates a suitable site basic environment by grading the slopes and carefully constructing platforms and circular drainage ditches; accurately mixes and applies special soil conditioners, cooperates with deep plowing and covering operations, and deeply improves the soil texture; carefully selects sea buckthorn, Chinese pine, Caragana seedlings and Astragalus seeds, and after soaking in a special mixed bacterial solution, mixes them in the slope and platform area according to a scientific and reasonable proportion; strictly implements a regular irrigation system in the early stage of planting, and continuously carries out all-round monitoring and flexible maintenance measures in the later stage. This series of interlocking, innovative and systematic steps aims to fully restore the physical structure and fertility level of the soil, successfully rebuild the vegetation community, and finally achieve the comprehensive ecological restoration of the open-pit coal mine dump, effectively reverse the ecological imbalance caused by mining activities, steadily promote the dump ecosystem to a stable and healthy road, greatly reduce the adverse impact on the surrounding ecological environment, and significantly improve the overall ecological benefits and environmental quality.

[0031] In a first aspect, the present application provides an ecological restoration method for an open-pit coal mine dump, the restoration method comprising the following steps: S1. The slopes of the dump are graded, and platforms are set between the slopes of each level, and the platforms are compacted; a circular drainage ditch is set at the bottom of the entire dump to collect excess water seeping from the dump and drain it to the treatment pool; S2. Apply soil conditioner to the platform area and slope, deep plow and cover the soil; S3. Select seedlings of seabuckthorn, Chinese pine, Caragana korshinskii and seeds of Astragalus membranaceus, and soak the roots of the seedlings of seabuckthorn, Chinese pine and Caragana korshinskii in a mixed bacterial solution composed of arbuscular mycorrhizal fungi and Trichoderma for 12-18 hours. The volume ratio of arbuscular mycorrhizal fungi to Trichoderma in the mixed bacterial solution is 2-4:1, and the spore concentration of both fungi is 5×10 7 - 3×10 8 cfu / mL; S4. Plant seabuckthorn and Astragalus astragali in a ratio of 3-5:1-2 on the slope, and plant Pinus tabulaeformis, Caragana microphylla and Astragalus astragali in a ratio of 1-3:2-4:1-2 on the platform area; S5. In the first three months after planting, irrigation should be carried out every half a month, with each irrigation volume of 20-30 cubic meters per hectare. After that, the irrigation frequency and water volume should be adjusted appropriately according to the precipitation conditions. S6. Regularly monitor the growth of vegetation and adjust maintenance measures in a timely manner according to the monitoring results. In step S1, this application first grades the slope and sets up a platform and a circular drainage ditch, which solves the problem of soil loss and soil erosion caused by the terrain and poor drainage in the dump, and stabilizes the site environment. In step S2, a soil conditioner composed of blast furnace slag, rice husk charcoal, chicken manure organic fertilizer, peat soil, potassium sulfate and a specific composite bacterial agent is applied and deep plowing and covering the soil is carried out. Blast furnace slag improves soil structure, rice husk charcoal improves water and fertilizer retention, chicken manure organic fertilizer provides rich nutrients, peat soil enhances fertility and water retention, potassium sulfate supplements potassium, and composite bacterial agents optimize soil microecology, thereby effectively improving the physical and chemical properties of the soil, improving soil fertility, and laying a good foundation for vegetation growth. In step S3, the roots of sea buckthorn, Chinese pine, and Caragana seedlings are soaked in a specific mixed bacterial solution to enhance the symbiotic relationship between the seedling roots and beneficial fungi, and improve their adaptability and nutrient absorption capabilities in harsh soil environments. In step S4, specific plants are planted in a mixed manner on the slope and platform areas according to specific proportions, and the ecological characteristics of different plants are utilized, such as the windbreak and soil fixation of sea buckthorn and Pinus tabulaeformis, the soil improvement of Caragana microphylla, and the rapid coverage and nitrogen fixation of Astragalus membranaceus, to promote the stable construction of vegetation communities. In step S5, regular irrigation in the early stage ensures the water demand of the initial growth of plants, and regular monitoring and timely maintenance measures in step S6 can be dynamically adjusted according to vegetation growth and soil changes to ensure the effectiveness and sustainability of the entire ecological restoration process. Through this series of steps, the problems of poor soil structure, low fertility, and difficulty in vegetation growth in the open-pit coal mine dump were successfully solved, the physical structure and fertility of the soil were restored, a stable vegetation community was rebuilt, the ecological imbalance caused by mining was effectively improved, and the dump ecosystem was promoted to develop in a stable and healthy direction, reducing the negative impact on the surrounding environment and improving the overall ecological benefits.

[0032] The scheme of the present application is described below in conjunction with the following specific examples. Unless otherwise specified, the raw materials used in the following examples are all from common commercial products, and the devices or equipment used are all purchased from conventional market sales channels.

[0033] Example 1 This embodiment provides an ecological restoration method for an open-pit coal mine dump, the restoration method comprising the following steps: S1. The slope of the open-pit coal mine dump is graded, with each level of slope height set to 4 meters and the platform width between each level of slope being 1.5 meters; a heavy roller is used to compact the platform to ensure that the compaction degree reaches 92%; a circular drainage ditch is set at the bottom of the entire dump, with a depth of 1.2 meters, a width of 1 meter, and a slope of 0.8%; S2. Prepare soil conditioner, the weight of each component of which is as follows: 60 parts of blast furnace slag, 30 parts of rice husk charcoal, 20 parts of chicken manure organic fertilizer, 15 parts of peat soil, 5 parts of potassium sulfate, and 0.5 parts of compound bacterial agent; the compound bacterial agent is composed of licheniformis, photosynthetic bacteria and lactic acid bacteria in a mass ratio of 3:2:2. Spread the soil conditioner evenly on the platform area and slope at a rate of 1200kg / hm², then deep plow to a depth of 30 cm, and finally cover with soil; S3. The roots of seabuckthorn, Chinese pine and Caragana korshinskii seedlings were immersed in a mixed bacterial solution composed of arbuscular mycorrhizal fungi and Trichoderma for 15 hours. The volume ratio of arbuscular mycorrhizal fungi to Trichoderma in the mixed bacterial solution was 3:1, and the spore concentration of both fungi was 2×10 8 cfu / mL; S4, the planting spacing of sea buckthorn is set to 2 meters, the planting spacing of Pinus tabulaeformis is set to 3.5 meters, the planting spacing of Caragana korshinskii is set to 1.5 meters, and the planting spacing of Astragalus membranaceus is set to 0.5 meters; sea buckthorn and Astragalus membranaceus are mixed and planted on the slope in a ratio of 4:1.5, and Pinus tabulaeformis, Caragana korshinskii and Astragalus membranaceus are mixed and planted in the platform area in a ratio of 2:3:1.5; in step S4 of this embodiment, before planting sea buckthorn, Pinus tabulaeformis and Caragana korshinskii, a layer of water retaining agent with a thickness of 4 cm is laid at the bottom of the planting pit, and the water retaining agent is polyacrylamide; S5. During the first three months after planting, irrigation should be carried out every half a month, with each irrigation volume of 25 cubic meters per hectare; S6. Regularly monitor the growth of vegetation.

[0034] Example 2 The difference between this embodiment and embodiment 1 is that the soil conditioner in step S2 of this embodiment has the following components by weight: 40 parts of blast furnace slag, 20 parts of rice husk charcoal, 15 parts of chicken manure organic fertilizer, 10 parts of peat soil, 3 parts of potassium sulfate, and 0.3 parts of composite bacterial agent; wherein the composite bacterial agent is composed of Bacillus licheniformis, photosynthetic bacteria and lactic acid bacteria in a mass ratio of 3:2:2. The remaining steps and parameters are consistent with those in embodiment 1.

[0035] Example 3 The difference between this embodiment and embodiment 1 is that the soil conditioner in step S2 of this embodiment has the following components by weight: 80 parts of blast furnace slag, 40 parts of rice husk charcoal, 30 parts of chicken manure organic fertilizer, 20 parts of peat soil, 8 parts of potassium sulfate, and 0.8 parts of composite bacterial agent; wherein the composite bacterial agent is composed of Bacillus licheniformis, photosynthetic bacteria and lactic acid bacteria in a mass ratio of 3:2:2. The remaining steps and parameters are consistent with those in embodiment 1.

[0036] Example 4 The difference between this embodiment and embodiment 1 is that in step S1 of this embodiment, an impermeable geotextile is laid on the inner wall of the annular drainage ditch to prevent water from seeping in and causing surrounding soil to collapse, and the drainage ditch is connected to a treatment pool equipped with water purification equipment.

[0037] Example 5 The difference between this embodiment and embodiment 4 is that in step S4, before planting sea buckthorn, Chinese pine and Caragana korshinskii, a layer of water retaining agent with a thickness of 4 cm is laid on the bottom of the planting pit, and the water retaining agent is bentonite.

[0038] Example 6 The difference between this embodiment and embodiment 4 is that in step S4, before planting sea buckthorn, Chinese pine and Caragana korshinskii, a layer of water retaining agent with a thickness of 4 cm is laid on the bottom of the planting pit, and the water retaining agent is starch.

[0039] Example 7 The difference between this embodiment and embodiment 4 is that in step S4, before planting sea buckthorn, Chinese pine and Caragana korshinskii, a layer of water retaining agent with a thickness of 4 cm is laid at the bottom of the planting pit, and the water retaining agent includes 50 parts of polyacrylamide, 25 parts of starch and 15 parts of bentonite by weight;

[0040] Example 8 The difference between this embodiment and embodiment 7 is that in step S4 of this embodiment, before planting sea buckthorn, Chinese pine and Caragana korshinskii, a layer of water retaining agent with a thickness of 4 cm is laid on the bottom of the planting pit.

[0041] The water retaining agent comprises 50 parts of cross-linked polyacrylamide, 25 parts of starch graft copolymer, and 15 parts of bentonite nanoparticles by weight; The preparation method of the water retaining agent is as follows: 50 parts of cross-linked polyacrylamide and 25 parts of starch graft copolymer are evenly mixed, and then 15 parts of bentonite nanoparticles are added and stirred at a speed of 250 rpm for 20 minutes to obtain a modified water retaining agent.

[0042] The preparation of cross-linked polyacrylamide is as follows: acrylamide monomer is dissolved in deionized water to prepare a solution with a mass concentration of 25%. Under nitrogen protection, a cross-linking agent N,N'-methylenebisacrylamide is added in an amount of 0.08% of the mass of the acrylamide monomer. At the same time, an initiator ammonium persulfate and an accelerator tetramethylethylenediamine are added to initiate a polymerization reaction. The reaction temperature is controlled at 35°C and the reaction time is 3 hours. After the reaction is completed, the solution is washed, impurities are removed, and the solution is dried to obtain cross-linked polyacrylamide.

[0043] The preparation of starch graft copolymer is as follows: starch is dispersed in deionized water to prepare a starch emulsion with a mass concentration of 12%, acrylic acid monomer is added under stirring, and its amount is 1.5 times the mass of starch, and then initiator potassium persulfate is added, and its amount is 0.8% of the mass of acrylic acid monomer. Graft copolymerization reaction is carried out at 65°C for 4 hours. After the reaction is completed, it is cooled and the pH value is adjusted to 7.5, and then ethanol precipitation is used, filtration, and drying are carried out to obtain starch graft copolymer.

[0044] The preparation of bentonite nanoparticles is as follows: the bentonite ore is crushed and passed through a 200-mesh sieve, the sieve material is dispersed in deionized water to prepare a suspension with a mass concentration of 8%, and a dispersant sodium hexametaphosphate is added under stirring, and its amount is 0.8% of the mass of the bentonite, and then ball milling is carried out in a ball mill with a ball-to-material ratio of 8:1 and a ball milling time of 5 hours. After the ball milling is completed, the product is centrifuged, the precipitate is collected, and it is repeatedly washed with deionized water to remove impurities and dried to obtain bentonite nanoparticles.

[0045] Example 9 The difference between this embodiment and embodiment 7 is that the water retaining agent in this embodiment includes 40 parts of cross-linked polyacrylamide, 20 parts of starch graft copolymer, and 10 parts of bentonite nanoparticles by weight. The rest is consistent with embodiment 4.

[0046] Example 10 The difference between this embodiment and embodiment 7 is that the water retaining agent in this embodiment includes 60 parts of cross-linked polyacrylamide, 30 parts of starch graft copolymer, and 10 parts of bentonite nanoparticles by weight. The rest is consistent with embodiment 4.

[0047] Comparative Example 1 The difference between this comparative example and Example 1 is that no soil conditioner is used in step S2 of this comparative example. The remaining steps and parameters are the same as those in Example 1.

[0048] Comparative Example 2 The difference between this comparative example and Example 1 is that this comparative example changes the plant mixing ratio. Step S4: The planting spacing of seabuckthorn is set to 2 meters, the planting spacing of Pinus tabulaeformis is set to 3.5 meters, the planting spacing of Caragana korshinskii is set to 1.5 meters, and the planting spacing of Astragalus astragali is set to 0.5 meters; seabuckthorn and Astragalus astragali are mixed and planted on the slope at a ratio of 1:1, and Pinus tabulaeformis, Caragana korshinskii and Astragalus astragali are mixed and planted on the platform area at a ratio of 1:1:1.

[0049] Comparative Example 3 The difference between this comparative example and Example 1 is that the seedlings of seabuckthorn, Chinese pine and Caragana in this comparative example are all replaced by seabuckthorn.

[0050] Comparative Example 4 The difference between this comparative example and Example 1 is that the seedlings of seabuckthorn, Chinese pine and Caragana in this comparative example are all replaced by Chinese pine.

[0051] Comparative Example 5 The difference between this comparative example and Example 1 is that the seedlings of seabuckthorn, Chinese pine and caragana in this comparative example are all replaced by caragana.

[0052] Comparative Example 6 This comparative example is a control experiment, and no restoration was performed on the open-pit coal mine spoil dump in this comparative example.

[0053] Experimental testing: After 2 years of restoration using the ecological restoration methods of Examples 1-10 and Comparative Examples 1-5, 50 sample plots (10m×10m) were set up in each restoration area. In each sample plot, the surface soil of about 0-2cm was collected by the S-type 5-point sampling method. After mixing evenly, sufficient samples were obtained by the quartering method and put into cloth bags. They were naturally air-dried in the laboratory. After one week, they were ground with a mortar and all passed through a 2mm sieve. The physical and chemical properties of the soil in different plots were measured: organic carbon, total nitrogen, total phosphorus, and heavy metal content (Cd: flameless atomic absorption method; Hg: cold atomic absorption method; As: diethyldithiocarbamate silver method; Pb: flame atomic absorption method; Cr: diphenylcarbazide colorimetric method). The soil organic carbon content was determined by external heating-potassium dichromate volumetric method; the total nitrogen content was determined by semi-micro Kjeldahl method, and the total phosphorus content was determined by perchloric acid-sulfuric acid digestion-molybdenum antimony colorimetric method; the specific soil physical and chemical index determination and analysis refer to the "Soil Agricultural Chemical Analysis Methods".

[0054] And detect the change rate of each test item.

[0055] Change rate = (test value three years after the experiment - test value of the control experiment) / test value of the control experiment.

[0056] The vegetation coverage two years after restoration was the ratio of the vertical projection area of ​​the vegetation canopy on the ground to the total land area. The results are shown in Table 1.

[0057] Table 1

[0058] Result analysis: Combined with the experimental test results in Table 1, it can be seen that by using the open-pit coal mine dump ecological restoration method in this application, especially the comprehensive application of multiple technical means shown in Examples 1-10, it is possible to effectively manage the complex ecological problems of the open-pit coal mine dump. Through in-depth analysis of each embodiment and comparative example, it can be seen that the open-pit coal mine dump ecological restoration method of this application has significant results.

[0059] In terms of soil improvement, the carefully configured soil conditioner ingredients and application amounts in Examples 1-3 inject vitality into the soil, and multiple nutrient supplements and structural optimization measures are carried out in parallel, effectively reshaping the soil microecology and laying a solid foundation for vegetation to take root and grow; the detailed design of the annular drainage ditch such as Example 4 and the application of various water-retaining agents in Examples 5-10 jointly build an efficient water management network, greatly reducing water loss and creating a stable water environment for plant growth.

[0060] Comparative Example 1 was in trouble because of the lack of soil conditioners. The soil was lacking in nutrients and had a stagnant structure, which made it difficult for vegetation to grow. The survival rate and growth trend were far less than those in the examples, and the vegetation coverage was also unsatisfactory, which profoundly highlighted the core position of soil conditioners. In terms of plant configuration, the scientific mixed planting strategy adopted in Example 1 and other examples showed strong advantages. Compared with the unreasonable mixed ratio in Comparative Example 2 and the single plant planting mode of Comparative Examples 3-5, it can effectively improve biodiversity, promote the steady development of plant communities, fully release ecological functions, strengthen the improvement efficiency of vegetation on soil, and improve the overall stress resistance of the ecosystem. The unrepaired barren scene of Comparative Example 6 clearly contrasts the outstanding value of the restoration method of this application, opens up a scientific and effective path for the ecological restoration of open-pit coal mine dumps, has great application potential and promotion value, and is expected to become a key force in improving the ecological problems caused by open-pit coal mining and achieving coordinated economic and ecological development, and effectively promotes the ecological restoration projects in related fields to a new height.

[0061] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for ecological restoration of an open-pit coal mine dump, characterized in that: The repair method comprises the following steps: S1. The slopes of the spoil dump are graded, platforms are set between the slopes of each level, and the platforms are compacted; a circular water collection ditch is set at the bottom of the entire spoil dump; S2. Apply soil conditioner to the platform area and slope, deep plow and cover the soil; S3. Select seedlings of seabuckthorn, Chinese pine, Caragana korshinskii and seeds of Astragalus membranaceus, and soak the roots of the seedlings of seabuckthorn, Chinese pine and Caragana korshinskii in a mixed bacterial solution composed of arbuscular mycorrhizal fungi and Trichoderma for 12-18 hours. The volume ratio of arbuscular mycorrhizal fungi to Trichoderma in the mixed bacterial solution is 2-4:1, and the spore concentration of both fungi is 5×10 7 - 3×10 8 cfu / mL; S4. Plant seabuckthorn and Astragalus astragali in a ratio of 3-5:1-2 on the slope, and plant Pinus tabulaeformis, Caragana microphylla and Astragalus astragali in a ratio of 1-3:2-4:1-2 on the platform area; S5. In the first three months after planting, irrigation should be carried out every half a month, with each irrigation volume of 20-30 cubic meters per hectare. After that, the irrigation frequency and water volume should be adjusted appropriately according to the precipitation conditions. S6. Regularly monitor the growth of vegetation and adjust maintenance measures in a timely manner based on the monitoring results.

2. The ecological restoration method according to claim 1, characterized in that: In step S2, the soil conditioner is composed of the following components in parts by weight: 40 - 80 parts of blast furnace slag, 20 - 40 parts of rice husk charcoal, 15 - 30 parts of chicken manure organic fertilizer, 10 - 20 parts of peat soil, 3 - 8 parts of potassium sulfate, 0.3 - 0.8 parts of compound bacterial agent; The composite bacterial agent consists of Bacillus licheniformis, photosynthetic bacteria and lactic acid bacteria in a mass ratio of 2-4:1-3:1-3.

3. The ecological restoration method according to claim 1, characterized in that: In step S4, the planting spacing of seabuckthorn is 1.8-2.2 meters, the planting spacing of Pinus tabulaeformis is 3-4 meters, the planting spacing of Caragana microphylla is 1.2-1.8 meters, and the planting spacing of Astragalus adoxaceae is 0.3-0.6 meters.

4. The ecological restoration method according to claim 1, characterized in that: In step S1, an impermeable geotextile is laid on the inner wall of the annular drainage ditch.

5. The ecological restoration method according to claim 1, characterized in that: In step S4, before planting sea buckthorn, Chinese pine and Caragana, a layer of water retaining agent with a thickness of 3 to 5 cm is laid at the bottom of the planting pit.

6. The ecological restoration method according to claim 5, characterized in that: The water retaining agent comprises the following components by weight: 40-60 parts of cross-linked polyacrylamide; 20-30 parts of starch graft copolymer; and 10-20 parts of bentonite nanoparticles.

7. The ecological restoration method according to claim 6, characterized in that: The preparation method of the cross-linked polyacrylamide is as follows: dissolving acrylamide monomer in deionized water to prepare a solution with a mass concentration of 20%-30%, adding a cross-linking agent N,N'-methylenebisacrylamide under nitrogen protection, wherein the amount thereof is 0.05%-0.1% of the mass of the acrylamide monomer, and simultaneously adding an initiator ammonium persulfate and an accelerator tetramethylethylenediamine to initiate a polymerization reaction, wherein the reaction temperature is controlled at 30-40°C, the reaction time is 2-4 hours, and after the reaction is completed, washing is performed to remove impurities and drying is performed to obtain the cross-linked polyacrylamide.

8. The ecological restoration method according to claim 6, characterized in that: The preparation method of the starch graft copolymer is as follows: starch is dispersed in deionized water to prepare a starch emulsion with a mass concentration of 10%-15%, acrylic acid monomer is added under stirring, and its amount is 1-2 times the mass of starch, and then initiator potassium persulfate is added, and its amount is 0.5%-1% of the mass of acrylic acid monomer. Graft copolymerization reaction is carried out at 60-70°C for 3-5 hours. After the reaction is completed, cooling is carried out, and the pH value is adjusted to 7-8, and then precipitation with ethanol is carried out, filtering, and drying are carried out to obtain the starch graft copolymer.

9. The ecological restoration method according to claim 6, characterized in that: The preparation method of the bentonite nanoparticles is as follows: the bentonite ore is crushed and then passed through a 200-mesh sieve, the sieve material is dispersed in deionized water to prepare a suspension with a mass concentration of 5%-10%, sodium hexametaphosphate as a dispersant is added under stirring, and the amount thereof is 0.5%-1% of the mass of the bentonite, and then ball milling is performed in a ball mill with a ball-to-material ratio of 5:1-10:1 and a ball milling time of 4-6 hours. After the ball milling is completed, the product is centrifuged, the precipitate is collected, and it is repeatedly washed with deionized water to remove impurities and dried to obtain the bentonite nanoparticles.

10. The ecological restoration method according to claim 6, characterized in that: The preparation method of the modified water-retaining agent is as follows: cross-linked polyacrylamide and starch graft copolymer are mixed evenly, and bentonite nanoparticles are added and stirred at a speed of 200-300 rpm for 15-30 minutes to obtain the modified water-retaining agent.

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