Method for repairing coal gangue area through plant-microorganism combination without foreign soil

Abstract

The invention provides a method for repairing a coal gangue area without foreign soil by utilizing plant-microorganism combination, and aims to form a self-sustaining repairing system through plant planting and biological characteristics and circulation of root exudate-microorganism metabolism of microorganisms, so that the ecological environment of the coal gangue area is effectively improved, vegetation recovery is promoted, and leaching water pollution is reduced. According to the method, the characteristics of rapid growth, high stress resistance, large biomass, good soil improvement effect and the like of the Juncao are fully utilized, a large amount of litters are produced through multiple times of cutting and laying, then a soil-like matrix is formed, the barren soil structure of the coal gangue area is improved, and conditions are created for subsequent plant community succession; meanwhile, green coverage can be quickly formed by matching with climbing characteristics of climbing plants, visual pollution of a coal gangue area is improved, and the landscape of a mining area is improved. The method provides a new thought and technical means for the treatment of the coal gangue area.

Description

Technical Field

[0001] The present invention belongs to the technical field of mine ecological restoration, and specifically relates to an ecological management method for repairing coal gangue areas through the synergistic action of plants and microorganisms without the introduction of foreign soil. The method is suitable for in-situ restoration of coal gangue areas with strong acidity, heavy metal enrichment, and poor water retention. Background Art

[0002] Gangue areas are formed by the long-term accumulation of solid waste generated during coal mining and washing, posing multiple environmental, ecological, health, and socioeconomic risks. Gangue often contains a variety of heavy metals and sulfides, which leach into the soil or groundwater through rainwater, polluting water sources. Gangue areas are loosely structured and prone to collapse during heavy rain or earthquakes, triggering geological disasters. Gangue's poor physical and chemical properties (high salt content, low nutrients, and toxic substances) inhibit plant growth, leading to extremely low vegetation cover, reduced plant and animal populations, decreased biodiversity, and declining ecosystem functions.

[0003] Coal gangue areas are prone to forming an acidic environment due to long-term accumulation, with high heavy metal content, loose surface structure and poor nutrients. The traditional soil import method requires transporting a large amount of soil, which is costly and damages the local ecological environment. Existing technologies include: limited adaptability of microbial communities: While guest-soil-free technologies centered around composite microorganisms (such as iron-reducing bacteria and sulfate-reducing bacteria) can inhibit gangue spontaneous combustion and promote vegetation restoration, their microbial activity is susceptible to the extreme environmental conditions of gangue areas (such as high acidity, high temperatures, and heavy metal pollution), resulting in unstable remediation efficiency; insufficient capacity to handle extreme environments: Sulfide oxidation often leads to a highly acidic environment (low pH) and heavy metal dissolution in gangue areas, while existing technologies have limited long-term neutralization and fixation of extreme pH or high concentrations of pollutants, requiring reliance on chemical adjuvants, increasing cost and complexity; and incomplete soil structure and nutrient improvement: Gangue particles are coarse and have low porosity. When used alone or mixed with a small amount of substrate, they have poor water and nutrient retention, easily causing plant growth decline in the later stages and making it difficult to form a sustainable ecological community. The present invention achieves efficient in-situ remediation of gangue areas by synergizing plants and microorganisms, combined with substrate improvement and post-processing management techniques. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for repairing coal gangue areas without guest soil by using a combination of plants and microorganisms, and a method for comprehensively treating coal gangue areas without guest soil by using plants with significantly different biological characteristics such as mushroom grass and climbing plants (ivy, creeper, clematis, Euonymus fortunei, wisteria, etc.) in combination with microbial fertilizers.

[0005] To achieve the above object, the present invention adopts the following technical solutions: Technical solution: 1. Plant screening and configuration 1.1 Pioneer Plants Select acid-resistant and barren-resistant deep-rooted plants such as Juncao (including giant Juncao, purple elephant grass, Oasis No. 1 Reed, Oasis No. 3 Reed, Oasis No. 6 Reed, Fucao No. 2, and Fucao No. 6), whose root secretions can promote the reproduction of microorganisms; Juncao can grow in the harsh soil environment of coal gangue areas. Even if the soil fertility is low and heavy metal pollution is serious, it can still survive and form dense vegetation 3 months after planting, effectively reducing dust in coal gangue areas and improving local microclimate; dense vegetation cover can reduce direct sunlight and lower the surface temperature of the gangue mountain. The root system and litter layer can reduce the entry of air into the interior of the coal gangue area, inhibit oxidation reactions, and reduce the risk of spontaneous combustion in the coal gangue area; Juncao grows fast and has a large biomass. A large amount of litter can increase soil organic matter, form a soil-like matrix, improve the poor soil structure in the coal gangue area, and create conditions for subsequent plant community succession.

[0006] 1.2 Companion Plants Paired with climbing plants (ivy, creeper, clematis, iris, wisteria, etc.), they can withstand a certain degree of extreme environment. The structure of the gangue area is loose and easily eroded by rain. The climbing characteristics of climbing plants can quickly cover the surface, and the dense leaves can lower the surface temperature and reduce the risk of spontaneous combustion in the gangue area. Climbing plants are evergreen all year round and can quickly form green cover, improve the visual pollution in the gangue area, and enhance the landscape of the mining area.

[0007] 2. Construction of Juncao Nitrogen-Fixing Fertilizer Juncao nitrogen-fixing bacterial fertilizer contains two strains of bacteria: Klebsiella oxytoca, which has the function of nitrogen fixation, and Bacillus mucilaginosus, which has the function of heavy metal passivation, with a mass ratio of 1:1. Klebsiella oxytoca can convert nitrogen (N2) in the air into ammonium nitrogen (NH4) that can be used by plants through nitrogenase. + ), improve soil fertility and reduce dependence on chemical nitrogen fertilizers; Bacillus subtilis secretes extracellular polysaccharides to fix heavy metals.

[0008] The nitrogen-fixing bacterial fertilizer of Juncao was prepared according to the literature "Effects of reducing chemical fertilizer and applying nitrogen-fixing bacterial fertilizer of Juncao on the growth, nutritional quality and soil nutrients of giant Juncao" (Jia Yulei, Liao Zhen, Wang Lifang, et al. Acta Prataculturae Sinica, 2021, 30 (3): 215-223). The specific preparation method includes: inoculating a mixed bacterial liquid of activated Klebsiella oxytoca and Bacillus subtilis in a mass ratio of 1:1 into LB liquid medium (5 g yeast extract, 10 g peptone, 10 g sodium chloride, distilled water to 1 L), and incubating at 30 ° C and 150-180 r·min. -1 The cells were cultured with shaking until the logarithmic growth phase.

[0009] 3. Joint repair steps Step 1: Improvement of substrate formula and seedling cultivation Use a mixture of loose, well-drained humus soil and Juncao nitrogen-fixing fertilizer (1:1 by mass) as the seedling medium. Select biodegradable seedling bags with a diameter of 5-40 cm, fill them with the medium, compact them, and arrange them in a regular pattern in the nursery shed. For Juncao, select grass stalks that are at least 8 months old, have strong buds, and are pest-free. Cut them into single-bud seed stems. Cut the top 2-3 cm above the bud flatly, and make a horse-ear-shaped cut 3-5 cm below the bud at the cutting end. Before planting, water the seedling medium thoroughly. When the soil is slightly dry and no longer sticky, plant the cuttings. The ideal depth should be to cover the axillary buds on the stem by 1 cm. Water immediately after planting. Juncao seedlings can be transplanted when they have 4-6 tillers. For climbing plants, sow seeds and cover them lightly with seedling medium (about 0.5 cm). Transplant when the seedlings reach 20-30 cm in height.

[0010] Step 2: Planting Intercropping is done in a ratio of "juncao:climber" (N:1, where 1≤N≤20). This means planting N rows of juncao followed by one row of vines, and so on. The specific steps include: 1) Planting in holes along fish-scale contour lines, with a row spacing of 200cm x 100cm, a hole depth of 30cm, and a hole diameter of 25cm; 2) Vertically placing the seedlings into the holes (without removing the bags), then covering with coal gangue slag and compacting; 3) Watering thoroughly after planting to establish rooting.

[0011] Step 3: Maintenance A drip irrigation system is installed; after planting, the mushroom grass needs to be mowed regularly and spread evenly on the coal gangue.

[0012] Technical effects: Synergistic Effect: The Klebsiella oxytoca and Bacillus colloids in the Juncao nitrogen-fixing bacterial fertilizer form a symbiotic relationship with the Juncao root secretions through metabolic feedback. Sugars, organic acids, and amino acids secreted by the Juncao roots provide carbon and energy sources for both types of microorganisms, stimulating their activity. Klebsiella oxytoca converts atmospheric nitrogen into ammonium nitrogen through nitrogen fixation, while Bacillus colloids releases insoluble nutrients in the soil through phosphorus and potassium solubilization. The two work together to enhance the availability of rhizosphere nutrients. At the same time, plant hormones such as auxin and cytokinin, along with organic acids produced by microbial metabolism, further promote the development of the Juncao root system and enhance the intensity of secretion release, forming a positive feedback loop of "root secretions-microbial activation-nutrient supply-plant growth," significantly improving soil fertility and plant stress resistance.

[0013] Ecological benefits: Leaching water is reduced by 60%-85% within 6 months, the effective state of heavy metals is reduced by 50%-65%, and biodiversity is increased by more than 100%; Low cost: No imported soil is required, and the repair cost is reduced by more than 50% compared with traditional methods.

[0014] Innovation: Plant-microbe feedback mechanism: Through the cycle of root exudates and microbial metabolism, a self-sustaining repair system is formed.

[0015] Improvement of substrate formula: In view of the environmental characteristics of coal gangue areas, functional bacteria are added to prepare mushroom grass nitrogen-fixing fertilizer to form a special substrate to improve the ability to retain water and fertilizer and passivate heavy metals.

[0016] Management innovation: Taking advantage of the fast growth and large biomass of Juncao, a large amount of litter is produced through multiple mowing and spreading, which in turn forms a soil-like matrix in the gangue area, improves the poor soil structure in the gangue area, and creates conditions for subsequent plant community succession.

[0017] The significant advantages of the present invention are: The present invention utilizes a combination of plants and microorganisms to repair coal gangue areas without foreign soil. This planting model can quickly increase the vegetation coverage in the coal gangue area, effectively enhance the water and fertilizer retention capacity of the coal gangue, and reduce soil erosion and leaching of pollutants. At the same time, the management technology of the present invention produces a large amount of dead matter by repeatedly mowing the mushroom grass and spreading it flat, thereby forming a soil-like matrix in the coal gangue area, improving the soil structure, reducing the leaching of rainwater to the coal gangue, and reducing the harmful effects of leached water on the natural environment.

[0018] Experiments have shown that compared with the blank control group, the leached water volume of the experimental group decreased by 65.0%, with a significant difference (P < 0.05). The total hardness and sodium content of the leached water in the experimental group were the lowest, with significant differences (P < 0.05). The manganese content in the leached water of the experimental group was significantly different from that of the control group (P < 0.05). This demonstrates that the plant-microorganism combined remediation technology of the present invention is helpful for the restoration of coal gangue areas without foreign soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the restoration effect diagram of Application Example 1; Figure 2 This is the repair effect diagram of Application Example 2. DETAILED DESCRIPTION

[0020] To make the above features and advantages of the present invention more clearly understood, the following embodiments are given for detailed description. Unless otherwise specified, the methods of the present invention are all conventional methods in the art.

[0021] A method for remediating coal gangue areas using plant-microorganism combined with no foreign soil comprises the following steps: Step 1: Improvement of substrate formula and seedling cultivation Use a mixture of loose, breathable, well-drained humus soil and Juncao nitrogen-fixing fertilizer as the seedling medium. Put the seedling medium into a degradable seedling bag, compact it, and arrange it in the seedling shed. For Juncao, use grass stalks that have grown for more than 8 months, have strong buds and are free of pests and diseases, cut into seed stems with one bud, cut the upper end flat 2 to 3 cm above the bud, and cut a horse ear-shaped incision 3 to 5 cm below the bud at the cutting end. Before cutting, water the seedling medium until it is soaked. When the soil is slightly dry and does not stick to your hands, cut the cuttings. The cutting depth should cover the axillary buds on the upper part of the seed stem by 1 cm. Water immediately after cutting. Transplant the Juncao seedlings when they have 4 to 6 tillers. Sow seeds for climbing plants, cover them with a seedling medium with a thickness of 0.5 cm, and transplant them when the seedlings grow to 20 to 30 cm. Step 2: Planting The intercropping ratio is 5:1, that is, five rows of Juncao are planted followed by one row of climbing plants, and so on. The specific steps include: 1) Planting in holes along the fish-scale contour lines, with a row spacing of 200cm x 100cm, a hole depth of 30cm, and a hole diameter of 25cm; 2) Place the seedlings vertically into the hole without removing the bag, then cover with coal gangue slag and compact it; 3) Water thoroughly after planting to establish rooting; Step 3: Maintenance A drip irrigation system is installed; after planting, the mushroom grass needs to be mowed regularly and spread flat on the coal gangue.

[0022] Preferably, the mass ratio of humus soil to nitrogen-fixing fungus fertilizer of Juncao in step 1 is 1: 1. The diameter of the degradable seedling bag is 20 cm.

[0023] Example 1 1 Materials and Methods 1.1 Test materials The mushroom grass used was the giant mushroom grass provided by the National Mushroom Grass Engineering Technology Research Center of Fujian Agriculture and Forestry University, and the climbing plant used was ivy.

[0024] 1.2 Overview of the pilot area In March 2023, a coal gangue area was selected for testing in Xipi Village, Gaopi Town, Yongding District, Longyan City, Fujian Province. Yongding District has a subtropical maritime monsoon climate with a mild year-round climate, an average annual temperature of 20.1°C, a frost-free period of 300 days, and an average annual rainfall of approximately 1,647 mm, with relatively concentrated rainfall. The test site is an abandoned coal mine site with a large amount of coal gangue accumulated, forming a gangue mountain. Due to the steep slope, large amounts of leached water runoff during rains pollute the environment.

[0025] 1.3 Experimental Design Nine projection areas of 30m2 were built at the test site. 2The plots were 10 m × 3 m, with a slope of approximately 25°. Each plot was divided by cement slabs and connected to a 3 m × 1 m × 1 m drainage basin at the bottom to collect runoff within the plot. The experiment included three treatments (with a 5:1 intercropping ratio of "juncao:climbing plant"): ① Experimental Group A (modified seedling medium, according to the present invention); ② Experimental Group B (conventional seedling medium, pure humus soil); and ③ a blank control. Each treatment had three replicates, with a plant spacing of 200 cm × 100 cm. Observation period was from June to August 2023, with leaching water statistics collected at the end of each month for each plot.

[0026] 1.4 Index determination (1) Water volume measurement: At the end of each month, measure the runoff pool, read the water level gauge, record the water volume, and then empty it.

[0027] (2) Water quality determination: Water samples were collected at the end of August 2023 to test the total hardness, manganese, sodium content and pH of the leached water.

[0028] 1.5 Data Analysis Data analysis was performed using Excel 2016 data processing system and Graphpad Prism software.

[0029] 2 Results and Analysis 2.1 Effects of different treatments on leaching water volume The determination and analysis results of leaching water volume under different treatments in the experimental site from June to August 2023 are shown in Table 1.

[0030] Table 1 Leaching water volume in different treatment plots from June to August 2023 As can be seen from Table 1, compared with the control group, the leaching water volume of experimental group A and experimental group B decreased by 84.0% and 67.0%, respectively, with significant differences (P < 0.05), indicating that Juncao and climbing plants grow fast and have well-developed root systems, which can increase the vegetation coverage rate in the coal gangue area and have a good effect on water conservation; compared with experimental group B, the leaching water volume of experimental group A decreased by 51.5%, with significant differences (P < 0.05), indicating that a positive feedback loop was formed between Juncao nitrogen-fixing bacterial fertilizer and plants, which improved the water conservation effect.

[0031] 2.2 Effects of different treatments on leaching water quality The measurement and analysis results of the leaching water quality of different treatments in the experimental site in August 2023 are shown in Table 2.

[0032] Table 2 Leachate water quality determination in August 2023 As can be seen from Table 2, there were significant differences in the total hardness, sodium content, pH, and manganese content of the leached water between the experimental groups A and B and the control group (P < 0.05), indicating that the combination of Juncao and climbing plants can reduce the impact of rainwater on the gangue area through tall and dense ground plants. Juncao has a well-developed root system and can absorb more water, thereby reducing the leaching effect of rainwater on the gangue. At the same time, Juncao can also absorb pollutants in the water body, thereby reducing the harm of leached water to the natural environment. There were also significant differences in the total hardness, sodium content, pH, and manganese content of the leached water between the experimental groups A and B (P < 0.05), indicating that a positive feedback loop was formed between the Juncao nitrogen-fixing fertilizer and the plants, which improved the restoration effect.

[0033] Application Example 1: This application example takes the Banzhai Coal Mine in Xipi Village, Gaopi Town, Yongding District, Longyan City, Fujian Province as an example to provide a method for repairing coal gangue areas using plant-microorganism combined with no foreign soil.

[0034] Yongding District, Longyan City, Fujian Province, is rich in mineral resources, but large-scale mining in the past has damaged the local ecological environment. Coal mining in Yongding District reflects the traditional small, scattered, and chaotic characteristics of southern coal mines. This historical legacy of abandoned mines has created ecological and environmental problems, hindering local economic and social development and the development of an ecological civilization.

[0035] Starting in 2022, the research team of the National Juncao Center of Fujian Agriculture and Forestry University selected the Banzhai Coal Mine to conduct a trial on the treatment of coal gangue areas without foreign soil. The climbing plant used was ivy, and the specific implementation method and operation steps are shown in the above specific implementation method.

[0036] After six months of implementing the above steps, the height of giant grass is 2.0m to 2.5m, the ivy spreads 10m to 12m, and the vegetation coverage in the coal gangue area increases to 75% to 80%. The planting effect is good (such as Figure 1 The amount of leached water decreased by 84%; the available Mn content in the leached water decreased by 49%.

[0037] Application Example 2: This application example takes Wangjiazhai Village, Panjiazhuang Town, Xingren County, Qianxinan Buyi and Miao Autonomous Prefecture, Guizhou Province as an example to provide a method for repairing coal gangue areas using plant-microorganism combined with no guest soil.

[0038] Xingren County is rich in coal resources, but solid waste such as coal gangue produced during coal mining will form leaching water containing heavy metals and harmful substances under the erosion, leaching and soaking of rainwater, causing serious pollution to the surrounding environment.

[0039] Starting in April 2023, the research team from the National Juncao Center of Fujian Agriculture and Forestry University selected Xingli Coal Mine to conduct a trial on the treatment of a non-exported soil and gangue area. Parthenocissus tricuspidata was selected as the climbing plant, and the remaining specific implementation methods and steps are described in the above-mentioned specific implementation method.

[0040] After 10 months of implementation according to the above steps, the height of giant fungus grass is 3.5m to 3.7m, creeper spreads 12m to 15m, and the vegetation coverage in the coal gangue area is increased to more than 85%, with good planting effect (such as Figure 2 The amount of leached water decreased by 73%; the available Mn content in the leached water decreased by 61%.

[0041] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for remediating coal gangue areas using plant-microorganism combined with no foreign soil, characterized in that: The following steps are involved: Step 1: Improvement of substrate formula and seedling cultivation Use a mixture of loose, breathable, well-drained humus soil and Juncao nitrogen-fixing fertilizer as the seedling medium. Place the seedling medium into degradable seedling bags, compact them, and arrange them in the seedling shed. For Juncao, use grass stalks that have grown for more than 8 months, have strong buds and are free of pests and diseases, cut into seed stems with one bud, cut the upper end flat 2 to 3 cm above the bud, and cut a horse ear-shaped incision 3 to 5 cm below the bud at the cutting end. Water the seedling medium until it is soaked before cutting. Cuttings should be made after the soil is slightly dry and no longer sticky. The cutting depth should be 1 cm to cover the axillary buds on the upper part of the seed stem. Water immediately after cutting. Transplant the Juncao seedlings when they have 4 to 6 tillers. Climbing plants are sown with seeds, and shallowly covered with a seedling medium with a thickness of 0.5 cm. Transplant the seedlings when they grow to 20 to 30 cm. Step 2: Planting Intercropping is done in rows with a ratio of "juncao:climbing plant = N:1, where 1≤N≤20," meaning that N rows of juncao are planted followed by one row of climbing plant, and so on. The specific steps include: 1) Planting in holes along fish-scale contour lines, with a row spacing of 200 cm × 100 cm, a hole depth of 30 cm, and a hole diameter of 25 cm; 2) Place the seedlings vertically into the hole without removing the bag, then cover with coal gangue slag and compact it; 3) Water thoroughly after planting to establish rooting. Step 3: Maintenance A drip irrigation system is installed; after planting, the mushroom grass needs to be mowed regularly and spread flat on the coal gangue.

2. The method according to claim 1, characterized in that The mass ratio of humus soil and nitrogen-fixing fungus fertilizer in step 1 is 1:

1.

3. The method according to claim 1 or 2, characterized in that Juncao nitrogen-fixing bacterial fertilizer contains two strains of bacteria, Klebsiella acidophilus and Bacillus subtilis, with a mass ratio of 1:

1.

4. The method according to claim 1, wherein The diameter of the degradable seedling bag is 5-40cm.

5. The method according to claim 1, wherein Climbing plants include ivy, creeper, clematis, euonymus, and wisteria.

6. The method according to claim 1, characterized in that The mushroom grass includes one of giant mushroom grass, purple elephant grass, Oasis No. 1 reed bamboo, Oasis No. 3 reed bamboo, Oasis No. 6 reed bamboo, Fucao No. 2, and Fucao No. 6.

Images