Ionic type rare earth tailing restoration method

Abstract

The invention provides an ionic type rare earth tailing restoration method, and relates to the technical field of environment restoration. Through soil improvement, local dominant plant planting and rhizosphere growth-promoting bacteria reinforcement, the heavy metal content, acidity and soil fertility of the rare earth tailing area are improved, soil with reduced heavy metal content, reduced acidity and increased fertility is obtained, continuous growth of arbor-shrub-grass three-layer dominant plants on the rare earth tailing area is promoted, and the yield of the arbor-shrub-grass three-layer dominant plants is increased. And finally, effective repair of the rare earth tailings is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental restoration, and in particular relates to a method for restoring ionic rare earth tailings. Background Art

[0002] Rare earth is a non-renewable strategic resource, known as "industrial MSG", "industrial vitamins" and "the mother of new materials". It is widely used in various industries such as military, agriculture and forestry, metallurgy, petrochemical, electronics, ceramics, etc. Due to the importance and high value of rare earth, there was a situation of extensive mining in the 1980s, with everyone rushing to open mines and mining indiscriminately, which caused a huge waste of resources and caused serious ecological and environmental problems. For example, the content of some heavy metals in the soil of a rare earth mine tailings area in Guangdong Province obviously exceeded the soil environmental quality standard (GB 15618-1995). At the same time, the soil acidification degree was high and the surface was strongly acidic; the total nitrogen, total phosphorus, available nitrogen and available phosphorus in the soil were all at extremely scarce levels. At the same time, the tailings area caused regional waterlogging, soil erosion, vegetation destruction, soil desertification, landslides and other environmental problems. Therefore, soil remediation work in rare earth mine tailings areas is imminent.

[0003] At present, there are three methods for remediation of rare earth mine tailings: physical method, chemical method and ecological restoration method. The physical method mainly uses engineering measures such as soil replacement, soil solidification and physical separation to repair it. This method has high investment, large engineering volume, and is prone to cause secondary geological disasters. It has low feasibility and few engineering cases. The chemical method mainly uses chemical reagents to carry out ex situ leaching of the soil in the mining area to leach pollutants in the soil. This method is simple and has obvious effects in the short term, but it uses a large amount of chemical agents and produces a large amount of leaching wastewater. The cost is high and it is easy to cause secondary pollution. Ecological restoration has the advantages of low cost, low energy consumption and maintenance-free in the later stage. It can not only improve the landscape of the mining area, but also reduce toxic and harmful substances in the soil and reduce secondary geological disasters. However, the rare earth mine tailings area has the characteristics of high content of multiple heavy metals, strong acid, barrenness and desertification, which makes it difficult to build a good ecosystem and the restoration effect is poor.

[0004] The prior art discloses a method for combined above-ground and underground ecological restoration of ionic rare earth tailings, including seven steps: restoration species screening, rhizosphere growth-promoting bacteria screening, soil improvement, growth-promoting bacteria inoculation, soil seed bank construction, algae biocrust construction, and post-maintenance. The method reduces the acidity of the soil in the rare earth tailings area and improves various physical and chemical properties of the soil. However, the prior art only repairs soil barrenness, soil desertification, and soil acidification, and does not specifically treat heavy metals in the soil.

[0005] The prior art discloses a method for repairing rare earth tailings, including laying a clay anti-leakage layer, laying a soil modification layer, planting vegetation and other steps, so that the water content, organic matter content, and effective nitrogen, phosphorus and potassium content in the soil of the rare earth tailings mining area are significantly improved, and the pH value of the soil is adjusted to 6-8, and the concentration of heavy metal Pb in the soil can be significantly reduced. However, the prior art only repairs a single heavy metal Pb concentration, and there are multiple ionic heavy metals in ionic rare earth tailings, and it is obviously not enough to only treat heavy metal Pb.

[0006] It can be seen that the current remediation methods cannot meet the needs of remediation of rare earth mine tailings areas. It is urgent to develop a multi-method combined remediation method targeting the characteristics of rare earth mine tailings areas such as high content of multiple heavy metals, strong acidity, poor soil and desertification. Summary of the invention

[0007] In order to solve the above problems existing in the prior art, the primary purpose of the present invention is to provide an ionic rare earth tailings repair method in view of the characteristics of rare earth tailings areas such as high content of multiple heavy metals, strong acidity, barrenness and desertification.

[0008] Another object of the present invention is to provide an ionic rare earth tailings.

[0009] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0010] The present invention provides a method for repairing ionic rare earth tailings, comprising the following steps:

[0011] The tailings sand in the rare earth tailings area to be repaired shall be improved in turn and three layers of native dominant plants, namely trees, shrubs and herbs, shall be planted;

[0012] The soil improvement comprises the following steps: constructing an impermeable layer, conditioning the soil and covering the foreign soil;

[0013] The construction of the anti-seepage layer includes removing the tailings sand on the surface of the mining area and using a cement mortar layer to construct the anti-seepage layer;

[0014] The soil conditioning comprises adding a soil conditioner to the tailings sand to obtain conditioned tailings sand, and then covering the conditioned tailings sand on the surface of the impermeable layer to construct a soil improvement layer; the soil conditioner comprises quicklime, slaked lime, phosphate compounds, silicate compounds, activated carbon, humus, clay, straw ash and organic fertilizer;

[0015] The planting of native dominant plants comprises the following steps: planting three layers of native dominant plants, namely trees, shrubs and herbs, in the soil layer, and introducing rhizosphere growth-promoting bacteria;

[0016] The rhizosphere growth-promoting bacteria are obtained by enriching the microorganisms in the root soil of the native dominant plants in the rare earth tailings area to be repaired, and include mycorrhizal fungi, phosphorus-dissolving bacteria, nitrogen-fixing bacteria, heavy metal-tolerant bacteria, plant pathogen antagonistic bacteria and organic matter-degrading bacteria;

[0017] The trees include Pinus massoniana, the shrubs include Schima superba, and the herbaceous plants include at least one of Rhizoma Cibotii, Setaria viridis, Miscanthus sinensis and leguminous plants.

[0018] The present invention repairs the ionic rare earth tailings through measures such as soil improvement, planting of native superior plants, and strengthening of rhizosphere growth-promoting bacteria.

[0019] The soil in the rare earth tailings mining area is relatively poor, with serious soil erosion and no conditions for plant growth. In order to make the soil in the mining area suitable for plant growth, the soil in the mining area needs to be conditioned before sowing.

[0020] The present invention uses nine modifiers to synergistically improve the soil properties of rare earth tailings, among which:

[0021] Quicklime (Cao) releases heat when it meets water, and can react to produce slaked lime (Ca(OH)2). At the same time, it generates a lot of heat, which can kill some other bacteria and play a certain bactericidal role, making it easier for rhizosphere growth-promoting bacteria to become dominant colonies after being added later; the addition of slaked lime can instantly adjust the acidity and alkalinity of the soil, making the soil suitable for planting trees and shrubs. Both types of lime can react with heavy metal ions to generate metal precipitation, which plays a role in solidifying heavy metals.

[0022] Phosphate compounds and silicate compounds can jointly alleviate the toxicity of heavy metals and form water-insoluble precipitates with heavy metals, thus reducing the toxicity to plants. In addition, the two also have the following effects:

[0023] 1) Provide a variety of nutrients: Silicate: Silicon is an important component of plant structure, which helps to enhance the mechanical strength of plants, improve lodging resistance, and improve resistance to diseases and insect pests. Phosphate: Phosphorus is an indispensable element in plant growth and development, and is involved in energy metabolism, nucleic acid synthesis, and cell division and growth.

[0024] 2) Improve soil structure: Silicates: Silicates help promote the aggregation of soil particles, form a good soil structure, and improve the air permeability and water retention capacity of the soil. Phosphates: Phosphates can indirectly improve the structure and stability of the soil by promoting the development of the root system.

[0025] 3) Enhance plant stress resistance: Silicate: Silicon can be deposited in the epidermal cells of plants to form a siliceous protective layer, which increases the resistance of plants to drought, high temperature, salinity and other adversities. Phosphate: Phosphorus can improve the energy storage and transfer efficiency of plants, thereby enhancing the overall stress resistance of plants.

[0026] 4) Promote nutrient absorption: Silicate: Silicon can improve the morphology and function of plant roots and promote the root system's absorption of nutrients and water. Phosphate: Phosphorus is an important element for root development and energy metabolism, directly promoting root growth and nutrient absorption.

[0027] 5) Improve soil microbial activity: The combined action of silicates and phosphates can provide soil microorganisms with a suitable environment and sufficient nutrition, promote the reproduction and activity of beneficial microorganisms, and thus improve soil fertility.

[0028] Humus, rice straw ash and organic fertilizer provide the following functions: 1) Improve soil structure and fertility. Humus has water retention, rice straw ash contains potassium, and organic fertilizer has organic matter. 2) Promote microbial activity. Humus and organic matter mainly provide organic matter and carbon sources, and rice straw ash mainly provides a suitable soil environment. 3) Increase the buffering capacity of soil. 4) Promote the healthy growth of plants.

[0029] The nine improvers of the present invention all play an important role in improving the properties of rare earth tailings and are indispensable.

[0030] Preferably, the mass ratio of the soil conditioner to the tailings sand is 0.5-2: 2500-10000. More preferably, the mass ratio of the conditioner to the tailings sand is 1:5000.

[0031] Preferably, the mass ratio of quicklime, slaked lime, phosphate compound, silicate compound, activated carbon, humus, clay, straw ash and organic fertilizer in the soil conditioner is 0.5-2: 0.5-2: 0.1-0.4: 0.05-0.2: 0.15-0.6: 0.25-1.0: 1-4: 0.25-1.0: 0.1-0.4, more preferably 1: 1: 0.2: 0.1: 0.3: 0.5: 2: 0.5: 0.2.

[0032] Preferably, the silicate compound is selected from at least one of diatomaceous earth, calcium silicate and potassium silicate.

[0033] Preferably, the phosphate compound is selected from at least one of calcium hydrogen phosphate, diammonium phosphate and triammonium phosphate.

[0034] Preferably, the humus is selected from at least one of rice husks, pine needles and compost.

[0035] Preferably, the clay is selected from at least one of kaolin, montmorillonite and bentonite.

[0036] Preferably, the rice straw ash is prepared by fully burning rice straw.

[0037] Preferably, the organic fertilizer is selected from at least one of chicken manure, sheep manure and sawdust.

[0038] The present invention enriches rhizosphere growth-promoting bacteria from the root soil of local dominant plants, and selects rhizosphere growth-promoting bacteria with specific functions from them. By introducing rhizosphere growth-promoting bacteria with different functions, the tolerance of plants to heavy metals is improved, and the growth and formation of vegetation of plants in soil with high heavy metal content are promoted, which is beneficial to the soil remediation of rare earth tailings. Among them:

[0039] Mycorrhizal fungi can form a symbiotic relationship with plant roots, provide water and nutrients (especially phosphorus) to plants through the mycorrhizal structure, enhance plant tolerance to heavy metals, promote plant growth, and strengthen the immune system;

[0040] Phosphorus-dissolving bacteria can convert organic phosphorus in the soil into inorganic phosphorus that can be absorbed by plants, thereby enhancing the efficiency of phosphorus absorption and utilization by plants and increasing plant growth rate and biomass.

[0041] Nitrogen-fixing bacteria can convert nitrogen in the air into ammonia and nitrates that can be used by plants, providing nitrogen sources for plants, promoting plant growth and development, and increasing crop yields;

[0042] Heavy metal tolerant bacteria can survive in heavy metal polluted environments and resist the toxicity of heavy metals, thereby improving the soil environment and promoting plant growth;

[0043] Plant pathogen antagonists can compete with plant pathogens for living space and produce antimicrobial substances, thereby reducing the incidence of plant diseases and protecting the healthy growth of plants;

[0044] Organic matter-degrading bacteria can decompose organic matter in the soil, release the nutrients needed for plant growth, improve soil fertility and promote plant growth.

[0045] Preferably, the mycorrhizal fungus is Boletus.

[0046] Preferably, the phosphate-solubilizing bacteria are Bacillus.

[0047] Preferably, the nitrogen-fixing bacteria are rhizobia.

[0048] Preferably, the heavy metal tolerant bacteria is Pseudomonas.

[0049] Preferably, the plant pathogen antagonist is an arbuscular mycorrhizal fungus.

[0050] Preferably, the organic matter degrading bacteria are actinomycetes.

[0051] Preferably, the method of introducing rhizosphere growth-promoting bacteria includes seed soaking, soil application, root irrigation, rhizosphere coating or fertilizer blending, and more preferably seed soaking or soil application.

[0052] More preferably, the step of introducing rhizosphere growth-promoting bacteria includes: soaking the seeds of the herbaceous plant in a mixed bacterial solution of the rhizosphere growth-promoting bacteria, and / or spraying the mixed bacterial solution of the rhizosphere growth-promoting bacteria on the soil surface at the roots of the trees or shrubs after planting the trees or shrubs.

[0053] More preferably, the bacterial content in the mixed bacterial solution is 10 8 ~10 9 Bacteria / g.

[0054] More preferably, the ratio of the number of mycorrhizal fungi, phosphate-solubilizing bacteria, nitrogen-fixing bacteria, heavy metal-tolerant bacteria, plant pathogen antagonistic bacteria and organic matter-degrading bacteria is 35-55:15-25:15-25:2-8:2-8:2-8, more preferably 45:20:20:5:5:5.

[0055] More preferably, the application ratio of the herbaceous plant seeds and the mixed bacterial solution is 5 to 20 mL of the mixed bacterial solution per kilogram of seeds, and more preferably 10 mL of the mixed bacterial solution per kilogram of seeds.

[0056] More preferably, the usage ratio of the root soil of the tree or shrub and the mixed bacterial solution is 1 to 3 grams of the mixed bacterial solution per gram of soil, more preferably 1 gram.

[0057] Specifically, the enrichment comprises the following steps:

[0058] S1, extracting microorganisms in rhizosphere soil with physiological saline, transferring the extract into inorganic phosphorus solid culture medium for culturing, and obtaining bacterial flora;

[0059] S2, separating bacterial colonies, selecting bacterial colonies with specific functions according to the morphology of bacterial colonies, washing and disinfecting the fungal fruiting bodies, taking bacterial flesh tissue and placing it in a first culture medium for culture, and then inoculating it into a second culture medium for screening;

[0060] Among them, the first and second culture media for mycorrhizal fungi can be MMN medium or PDA medium; the inorganic phosphorus solid medium or King's B medium can be used for phosphate-solubilizing bacteria; the YMA medium or Asubei nitrogen-fixing medium can be used for nitrogen-fixing rhizobia; the LB medium with additional mixed metal salts can be used for metal-tolerant bacteria, and the metal ion types include Zn 2+ , Cu 2+ 、Ni 2+ , Pb 2+ 、Co 2+ Cr 3+ , Mn 2+, the concentration of each metal salt is 1mmol / L; the first culture medium for plant pathogen antagonistic bacteria is LB medium, and the second culture medium is PDA medium or YPD medium; the first culture medium for organic matter degrading bacteria is PDA medium, and the second culture medium is Gao's No. 1 medium.

[0061] The present invention selects specific types of native dominant plants to be planted according to the physical and chemical properties of the soil. The native dominant plants need to meet the following requirements: First, tolerance. Because the physical and chemical properties of the soil are poor, the native dominant plants must have strong acid and alkali resistance and high metal ion soil resistance, so that they can grow well; second, they can reduce the concentration of heavy metals in the soil, and at the same time have the ability to conserve water and soil, and gradually improve the physical and chemical properties of the soil; third, the types of dominant plants need to be diversified to build a multi-level maintenance-free plant restoration system. Single grasses, trees and shrubs are difficult to play a comprehensive role.

[0062] The specific comprehensive effects are as follows:

[0063] 1. Reduce soil erosion on slopes: Trees, shrubs and herbaceous plants stabilize the soil through their respective root structures. The deep roots of trees and the shallow roots of shrubs work together to prevent rainwater from directly impacting the soil surface, thereby reducing soil erosion caused by water flow.

[0064] 2. Increase the nutrient content of the soil: The dead branches and leaves and root secretions of plants can increase the organic matter in the soil. After decomposition, these organic matter can provide the nutrients needed for plant growth, while improving the soil structure and making it more suitable for plant growth.

[0065] 3. Enhance the strength of shallow soil: The comprehensive configuration of trees, shrubs and grasses can not only prevent the loss of surface soil, but also enhance the stability of the soil through the reinforcement effect of plant roots. This configuration mode is more effective, especially in areas with frequent rainfall or steep terrain.

[0066] Preferably, the slope protection guard is selected from at least one of Bermuda grass, tall fescue and ryegrass, and the leguminous plant is selected from at least one of astragalus, alfalfa and purple alfalfa.

[0067] The present invention constructs an impermeable layer at the bottom of the rare earth tailings area, which can prevent rainwater from seeping in and avoid toxic and harmful substances such as heavy metals from polluting deep soil and groundwater.

[0068] Preferably, the mortar is prepared from lime, clay and mineral sand in a mass ratio of (20-40): (30-50): (20-40).

[0069] More preferably, the thickness of the anti-seepage layer is 10 to 30 cm.

[0070] More preferably, after using the cement mortar covering layer, the cement mortar is compacted.

[0071] More preferably, the excavation depth is 1 to 1.5 m.

[0072] The invention covers the surface of the improved soil layer with foreign soil, which is beneficial to the growth of herbaceous plants and shrubs, so that a certain vegetation can be formed in the tailings area in a shorter time, thereby reducing soil and water loss.

[0073] Preferably, the method of covering the imported soil is horizontal paving. More preferably, the covering thickness of the imported soil is 20 to 50 cm.

[0074] Preferably, the soil improvement comprises the following steps: leveling the mining area, constructing an impermeable layer, conditioning the soil and covering the imported soil and constructing drainage facilities;

[0075] Preferably, the sowing comprises the following steps:

[0076] For herbaceous plants, draw a line with a width of 1.5 to 2 meters to make the soil surface flat, sow with a row spacing of 25 cm and a sowing width of 5 cm, cover with 1 cm of soil, and irrigate by slow irrigation; and / or,

[0077] For trees or shrubs, the plant spacing is 1.5m×1.5m, the pit diameter is 20cm larger than the diameter of the tree soil ball, the upper and lower parts of the pit are vertical, and the support is set up in the form of "three supports in one bundle".

[0078] The present invention also provides an ionic rare earth tailing, comprising:

[0079] An impermeable layer, the impermeable layer being arranged on at least a portion of the tailings sand layer;

[0080] a soil improvement layer, the soil improvement layer being arranged on at least a portion of the anti-seepage layer, the soil improvement layer comprising tailings sand and soil improvers, the soil improvers comprising quicklime, slaked lime, phosphate compounds, silicate compounds, activated carbon, humus, clay, straw ash and organic fertilizer;

[0081] a guest soil layer, the guest soil layer being disposed on at least a portion of the soil improvement layer;

[0082] Vegetation, the vegetation is planted on at least a part of the imported soil layer, the vegetation includes three layers of dominant plants of trees, shrubs and herbaceous plants, the tree is Pinus massoniana, the shrub is Schima superba, and the herbaceous plant is at least one of slope guard, Setaria viridis, Miscanthus sinensis and legumes.

[0083] Preferably, the mass ratio of quicklime, slaked lime, phosphate compound, silicate compound, activated carbon, humus, clay, straw ash and organic fertilizer is 0.5-2: 0.5-2: 0.1-0.4: 0.05-0.2: 0.15-0.6: 0.25-1.0: 1-4: 0.25-1.0: 0.1-0.4, and more preferably 1: 1: 0.2: 0.1: 0.3: 0.5: 2: 0.5: 0.2.

[0084] Preferably, the silicate compound is selected from at least one of diatomaceous earth, calcium silicate and potassium silicate.

[0085] Preferably, the phosphate compound is selected from at least one of calcium hydrogen phosphate, diammonium phosphate and triammonium phosphate.

[0086] Preferably, the humus is selected from at least one of rice husks, pine needles and compost.

[0087] Preferably, the clay is selected from at least one of kaolin, montmorillonite and bentonite.

[0088] Preferably, the rice straw ash is prepared by fully burning rice straw.

[0089] Preferably, the organic fertilizer is selected from at least one of chicken manure, sheep manure and sawdust.

[0090] Preferably, the mass ratio of the soil conditioner to the tailings sand is 0.5-2: 2500-10000. More preferably, the mass ratio of the soil conditioner to the tailings sand is 1:5000.

[0091] Preferably, the slope protection agent is selected from at least one of Bermuda grass, tall fescue and ryegrass. Preferably, the leguminous plant is selected from at least one of Chinese milk vetch, alfalfa and purple alfalfa.

[0092] Compared with the prior art, the present invention has the following beneficial effects:

[0093] The present invention improves the heavy metal content, acidity and soil fertility in the rare earth tailings area by improving the soil, planting native dominant plants and strengthening rhizosphere growth-promoting bacteria, thereby obtaining soil with reduced heavy metal content, reduced acidity and increased fertility, and promoting the continuous growth of three layers of dominant plants of trees, shrubs and grasses in the rare earth tailings area, thereby ultimately achieving effective remediation of rare earth tailings. BRIEF DESCRIPTION OF THE DRAWINGS

[0094] Figure 1 This is a comparison diagram before and after the rare earth tailings area is repaired using the method provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0095] The content of the present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present embodiment are conventional reagents, methods and equipment in the art.

[0096] All embodiments and comparative examples of the present invention adopt the following method to repair rare earth tailings:

[0097] 1. Soil improvement

[0098] (1) Leveling of the mining area: Use excavators and bulldozers to level the site.

[0099] (2) Ground anti-seepage: Mechanical excavation is used to a depth of 1m. The excavated tailings sand is moved to one side of the site, and then covered with cement mortar and compacted mechanically. The cement mortar includes lime, clay and mineral sand, wherein the mass ratio of lime, clay and mineral sand is 30:30:40, and the thickness of the compacted cement mortar anti-seepage layer is 15cm.

[0100] (3) Soil conditioning

[0101] Soil conditioners of different compositions and proportions are prepared. The soil conditioning depth of the tailings area is about 60cm, and the amount of soil conditioner added per hectare of tailings sand is 2.0 tons. The conditioned tailings sand is flattened by a bulldozer and covered with an anti-seepage layer.

[0102] (4) Covering with imported soil

[0103] The thickness of the imported soil cover is about 20cm to 50cm, and it should be flattened moderately.

[0104] (5) Drainage measures

[0105] The construction specifications of the concrete drainage channel are 0.40×0.40m, with 0.2m thick concrete poured on both sides and 0.15m thick plain concrete padding at the bottom of the ditch.

[0106] 2. Screening of local dominant plants

[0107] This tailings area uses a combination of tree, shrub and grass for planting. The tree is Pinus massoniana, the shrub is Schima superba, and grass seeds are sown between the rows. The grass seeds are mainly mixed grass seeds, mainly slope guards, Setaria viridis, and Miscanthus sinensis, supplemented by mixed legumes. Among them, slope guards are Cynodon dactylon, tall fescue and ryegrass, and the legumes are Chinese milk vetch, alfalfa and purple clover.

[0108] 3. Enrichment of rhizosphere growth-promoting bacteria

[0109] A certain amount of root soil is collected next to the local dominant plants, and the microorganisms therein are extracted and cultured. According to the morphology of the microorganisms, rhizosphere growth-promoting bacteria with specific functions such as mycorrhizal fungi, phosphorus-dissolving bacteria, nitrogen-fixing bacteria, heavy metal-tolerant bacteria, plant pathogen antagonists and organic matter-degrading bacteria are selected, cultured and enriched to a certain number, and all rhizosphere growth-promoting bacteria are mixed to obtain a mixed flora of rhizosphere growth-promoting bacteria. The mycorrhizal fungi used in all embodiments and comparative examples of the present invention are boletus, the phosphorus-dissolving bacteria are Bacillus, the nitrogen-fixing bacteria are rhizobia, the heavy metal-tolerant bacteria are Pseudomonas, the plant pathogen antagonists are arbuscular mycorrhizal fungi, and the organic matter-degrading bacteria are actinomycetes.

[0110] The specific steps are as follows:

[0111] Soil collection: Take the rhizosphere soil about 10 cm below the surface of local dominant plants, shrubs, and herbs, put it into a ziplock bag, quickly put it into a foam box filled with crushed ice, bring it back to the laboratory and store it in a refrigerator at 4°C for later use. Among them, the trees are Pinus massoniana, the shrubs are Schima superba, and the herbs are Setaria viridis and Miscanthus sinensis.

[0112] Separation: The rhizosphere soil of trees, shrubs, and herbs was cultured separately. Take 10g of rhizosphere soil, add 100mL of physiological saline, stir with an electromagnetic stirrer for 5min, let it stand for 15min, take the supernatant, dilute it by 100 times, take 50μL of the dilution and transfer it to the inorganic phosphorus solid culture medium plate, and spread it evenly with a triangular coating rod, and culture it in a 25℃ incubator. Observe the bacterial growth on the plate after 48h.

[0113] Purification: Use the plate streaking method to separate the bacterial colonies, and select the bacterial colonies with specific functions according to the morphology of the bacterial colonies. Select well-preserved large ECM fungal fruiting bodies, rinse them under running water until there is no dirt impurities on the surface, and rinse them under sterile water 5 times, 30 seconds each time; disinfect the surface of the fruiting bodies with 75% alcohol and transfer them to the sterile operating table, soak the fruiting bodies in beakers 1-5 with 250ml sterile water, 30 seconds each time; soak the fruiting bodies in beakers 6-7 with 250ml 75% alcohol, 30 seconds each time; then place the fruiting bodies in beakers 8-13 with 250ml sterile water and soak them, 30 seconds each time; use 121℃ high-pressure sterilized filter paper to absorb the moisture. Use an alcohol lamp sterilized A-type sterile knife to cut the large ECM fungus fruiting body in half to expose the flesh tissue at the connection between the cap and the stipe, then use a sterilized B-type sterile knife to cut the young flesh tissue inside the fruiting body that has not yet become lignified, and use a sterilized inoculation needle to pick up the flesh tissue and put it into the first medium plate that has been poured, and invert it in a 25°C constant temperature biochemical incubator to observe the mycelial growth of the flesh tissue in the plate every 2 days. After the mycelium grows vigorously, continue to inoculate it on the second medium plate for observation, and finally send the purified bacterial plate to Shanghai Meiji Biomedical Technology Co., Ltd. for strain ITS molecular identification.

[0114] The first and second culture media for mycorrhizal fungi can be MMN medium or PDA medium; inorganic phosphorus solid medium or King's B medium can be used for phosphate-solubilizing bacteria; YMA medium or Asubei nitrogen-fixing medium can be used for nitrogen-fixing rhizobia; LB medium with additional mixed metal salts can be used for metal-tolerant bacteria. The metal ion types include Zn 2+ , Cu 2+ 、Ni 2+ , Pb 2+ 、Co 2+ Cr 3+ , Mn 2+ , the concentration of each metal salt is 1mmol / L; the first culture medium for plant pathogen antagonistic bacteria is LB medium, and the second culture medium is PDA medium or YPD medium; the first culture medium for organic matter degrading bacteria is PDA medium, and the second culture medium is Gao's No. 1 medium.

[0115] 4. Plant cultivation

[0116] The planting was carried out by combining manual and soil spraying. 8 A mixed bacterial solution of rhizospheric growth-promoting bacteria with cells / gram.

[0117] (1) Herbaceous plant planting: 1 kg of seeds are sown per mu of herbaceous plants. Before sowing, soak the seeds in a mixed bacterial solution of rhizosphere growth-promoting bacteria for 5-8 hours. Soak 1 kg of seeds in 10 mL of mixed bacterial solution of rhizosphere growth-promoting bacteria, and sow after the surface moisture is dried. Draw a line with a width of 1.5 meters or 2 meters to open the soil. After the soil surface is leveled, the row spacing is 25 cm and the sowing width is 5 cm. Cover the soil with 1 cm after sowing, and irrigate slowly to soak the soil.

[0118] (2) Planting of trees and shrubs

[0119] Before sowing, spray the mixed bacterial flora solution of rhizosphere growth-promoting bacteria into the root cup at a rate of 1 gram of mixed bacterial flora solution of rhizosphere growth-promoting bacteria / gram of soil (10 8 The spacing between trees and shrubs is 1.5m×1.5m; the pit diameter is 20cm larger than the diameter of the tree soil ball, and the top and bottom of the pit should be vertical. Finally, the support is set up with "three supports in one bundle" as the main method.

[0120] 5. Continuous repair

[0121] The repair time is 1 year.

[0122] Table 1 Composition and ratio of each modifier in each embodiment and comparative example

[0123]

[0124]

[0125] Table 2 Composition and proportion of each rhizosphere growth-promoting bacteria in each embodiment and comparative example

[0126]

[0127]

[0128] The present invention uses the following analysis method to analyze the soil properties of the rare earth tailings area before and after restoration:

[0129]

[0130] Performance Testing

[0131] The effects of the composition and proportion of different amendments on soil properties and vegetation growth are shown in Table 3:

[0132] Table 3 Effects of composition and proportion of different amendments on soil properties and vegetation growth

[0133]

[0134]

[0135] The effects of the composition and proportion of different rhizosphere growth-promoting bacteria on soil properties and vegetation growth are shown in Table 4:

[0136] Table 4 Effects of the composition and proportion of different rhizosphere growth-promoting bacteria on vegetation growth

[0137]

Claims

1. A method for remediating ionic rare earth tailings, comprising the following steps: The tailings sand in the rare earth tailings area to be repaired shall be improved in turn and three layers of native dominant plants, namely trees, shrubs and herbs, shall be planted; The soil improvement comprises the following steps: Constructing impermeable layers, conditioning soil and covering imported soil; The construction of the anti-seepage layer includes removing the tailings sand on the surface of the mining area and using a cement mortar layer to construct the anti-seepage layer; The soil conditioning comprises adding a soil conditioner to the tailings sand to obtain conditioned tailings sand, and then covering the conditioned tailings sand on the surface of the impermeable layer to construct a soil improvement layer; the soil conditioner comprises quicklime, slaked lime, phosphate compounds, silicate compounds, activated carbon, humus, clay, straw ash and organic fertilizer; The planting of native dominant plants comprises the following steps: planting three layers of native dominant plants, namely trees, shrubs and herbs, and introducing rhizosphere growth-promoting bacteria; The rhizosphere growth-promoting bacteria are obtained by enriching the microorganisms in the root soil of the native dominant plants in the rare earth tailings area to be repaired, and include mycorrhizal fungi, phosphorus-dissolving bacteria, nitrogen-fixing bacteria, heavy metal-tolerant bacteria, plant pathogen antagonistic bacteria and organic matter-degrading bacteria; The trees include Pinus massoniana, the shrubs include Schima superba, and the herbaceous plants include at least one of Rhizoma Cibotii, Setaria viridis, Miscanthus sinensis and leguminous plants.

2. The repair method according to claim 1, characterized in that: The mass ratio of the soil conditioner to the tailings sand is 0.5-2:2500-10000.

3. The repair method according to claim 1, characterized in that: The mass ratio of quicklime, slaked lime, phosphate compound, silicate compound, activated carbon, humus, clay, straw ash and organic fertilizer is 0.5-2: 0.5-2: 0.1-0.4: 0.05-0.2: 0.15-0.6: 0.25-1.0: 1-4: 0.25-1.0: 0.1-0.

4.

4. The repair method according to claim 1, characterized in that: The silicate compound is selected from at least one of diatomaceous earth, calcium silicate and potassium silicate; the phosphate compound is selected from at least one of calcium hydrogen phosphate, diammonium phosphate and triammonium phosphate; the humus is selected from at least one of rice husks, pine needles and compost; the clay is selected from at least one of kaolin, montmorillonite and bentonite; the straw ash is prepared by fully burning rice straw; and the organic fertilizer is selected from at least one of chicken manure, sheep manure and sawdust.

5. The repair method according to claim 1, characterized in that: The mycorrhizal fungus is boletus; the phosphate-dissolving bacteria is Bacillus; the nitrogen-fixing bacteria is rhizobium; the heavy metal-tolerant bacteria is Pseudomonas; the plant pathogen antagonistic bacteria is arbuscular mycorrhizal fungi; and the organic matter-degrading bacteria is actinomycetes.

6. The repair method according to claim 1, characterized in that: The step of introducing rhizosphere growth-promoting bacteria includes: soaking the seeds of the herbaceous plant in a mixed bacterial solution of the rhizosphere growth-promoting bacteria; and / or, after planting trees or shrubs, spraying the mixed bacterial solution of the rhizosphere growth-promoting bacteria on the soil surface at the roots of the trees or shrubs.

7. The repair method according to claim 1, characterized in that: The slope protection agent is selected from at least one of bermudagrass, tall fescue and ryegrass, and the leguminous plant is selected from at least one of astragalus, alfalfa and purple alfalfa.

8. The repair method according to claim 1, characterized in that: The mortar is prepared from lime, clay and mineral sand in a mass ratio of (20-40): (30-50): (20-40).

9. The repair method according to claim 1, characterized in that: The soil improvement comprises the following steps: leveling the mining area, constructing an impermeable layer, conditioning the soil, covering the imported soil and building drainage facilities.

10. An ionic rare earth tailing, comprising: An impermeable layer, the impermeable layer being arranged on at least a portion of the tailings sand layer; a soil improvement layer, the soil improvement layer being arranged on at least a portion of the anti-seepage layer, the soil improvement layer comprising tailings sand and soil improvers, the soil improvers comprising quicklime, slaked lime, phosphate compounds, silicate compounds, activated carbon, humus, clay, straw ash and organic fertilizer; a guest soil layer, the guest soil layer being disposed on at least a portion of the soil improvement layer; Vegetation, the vegetation is planted on at least a part of the imported soil layer, the vegetation includes three layers of dominant plants of trees, shrubs and herbaceous plants, the tree is Pinus massoniana, the shrub is Schima superba, and the herbaceous plant is at least one of slope guard, Setaria viridis, Miscanthus sinensis and legumes.

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