In-situ soiling method for tailings in production and use tailings ponds and application of in-situ soiling method

Abstract

The invention relates to an in-situ soiling method for tailings of a mine tailing pond in use and application, and belongs to the resource utilization and ecological restoration technology of a tailing pond district, the in-situ soiling method comprises the following steps: step 1, leveling the tailings of the mine tailing pond in situ, turning over and loosening the tailings of 40cm on the surface layer, adding exogenous organic matters, and uniformly mixing to obtain a tailing matrix; 2, spraying a mine area soil plant rhizosphere bacterial liquid into the tailing matrix, and culturing in situ for 20-40 days to preliminarily form a soil-like matrix suitable for field planting of pioneer plants; 3, the pioneer herbaceous plants are sown, and functional microorganisms are inoculated. By means of the application of the method, all-season evergreen of reclamation vegetation in the in-use tailings pond and stable solidification and non-migration of heavy metal can be achieved, water and soil loss and environmental pollution of tailings are effectively controlled, and technical support is provided for large-area popularization of ecological restoration of non-ferrous metal tailings ponds in China.

Description

Technical Field

[0001] The invention relates to tailings resource utilization and ecological restoration technology, in particular to an in-situ soilization method and application of tailings in a tailings pond in production and use. Background Art

[0002] Tailings are byproducts produced during the development of mineral resources. They are produced in large quantities and their impact on the ecological environment cannot be ignored. Tailings are mainly produced during the mining and beneficiation of metal or non-metal mines. After valuable minerals are extracted, the remaining solid waste is the tailings. my country produces about 1 billion tons of tailings annually, accounting for a quarter of the annual production of general industrial solid waste. The storage of tailings not only occupies a large amount of land, but may also cause environmental pollution such as water, soil, and air around the mining area, soil erosion, vegetation destruction, and reduced biodiversity.

[0003] The main components of tailings include O, Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K, P and other elements. The content of these elements in different types of tailings varies greatly, and they have different crystallization phenomena. The main mineral types are primary minerals such as quartz, feldspar, chlorite, etc., and contain a small amount of difficult-to-extract metal minerals, such as pyrite and galena. With the improvement of mining technology, the degree of ore grinding has gradually increased. Generally, the flotation tailings have a particle size of about 75 μm, accounting for 40%-85%. The iron tailings treated by the regrinding and recycling process can reach a particle size of micron level.

[0004] The treatment of tailings in the existing technology is mainly based on resource utilization, for example, by recovering useful elements, preparing building materials, serving as goaf materials, as farmland improvers, etc. These methods can treat a certain amount of tailings, but the utilization rate is low, the cost is high, and it is difficult to industrialize. In addition, the tailings need to be transported from the mine to the processing and utilization area for secondary treatment, and the transportation cost is high. Due to the small particle size of the tailings, dust is easily generated during transportation and secondary treatment, and waste will still be generated, causing secondary pollution to the environment, which does not conform to the principles of resource utilization, reduction, and harmlessness.

[0005] There are some reports on in-situ remediation, mainly covering the tailings dump with soil to create farmland, but there are problems of high cost or poor effect. For example, CN109174935A discloses a method of using microbial agents and improvers to plant greenery on tailings. It relies on improvers composed of biochar, organic fertilizer, rice husks and expanded clay, as well as artificially cultivated specific microbial agents, resulting in higher labor and material costs, and relying on the introduction of a large amount of guest soil (mature soil that needs to be transported from other places). The patent does not quantitatively examine the soil formation degree of the tailings itself, and it is difficult to evaluate the degree of dependence of its final technical effect on the added guest soil. However, the dependence on the use of guest soil has undoubtedly greatly increased the cost.

[0006] It is necessary to develop economical, efficient, environmentally friendly and low-energy technology for in-situ resource utilization of tailings. Summary of the invention

[0007] Based on the needs and gaps in the above-mentioned fields, the present invention focuses on the modification of tailings matrix, vegetation selection and ecosystem reconstruction in the tailings ponds in production and use, and finally forms a tailings ecological restoration technology of "in situ matrix improvement + direct sowing of vegetation", that is, by adding a small dose of additional modifier, the physical structure and fertility conditions of the fine-grained tailings soil matrix are improved, so as to achieve conditions suitable for the long-term growth of plants, realize the evergreen vegetation of the tailings pond reclamation and the stable solidification and non-migration of heavy metals, effectively control the soil erosion and environmental pollution of tailings, and provide technical support for the large-scale promotion of ecological restoration of non-ferrous metal tailings ponds in my country.

[0008] Based on the above technical achievements, the present invention requests protection of the following technical solutions: 1. A method for in-situ soil treatment of tailings from a tailings pond in a production or use mine, characterized in that it comprises the following steps: Step 1. Level the tailings of the tailings pond of the mine in production and use in situ, plow and loosen the surface 40cm tailings (to facilitate the flow, sedimentation, mud and water separation and drainage of the tailings, and ventilation), add exogenous organic matter, and mix the tailings and the exogenous organic matter evenly to obtain a tailings matrix, wherein the exogenous organic matter refers to a mixture of biomass and biochar in a ratio of 1-2:1-2, and the weight ratio of the added amount of the exogenous organic matter to the tailings of the tailings pond is 3-8%; then, ridges are formed every 1.8-2 meters, leaving ridges with a width of 0.5-0.8 meters and a depth of 0.4-0.6 meters; Step 2. Spray the rhizosphere bacteria solution of the mining area soil plants in the tailings matrix and culture it in situ for 20 to 40 days, during which the water content is ensured to be 12 to 18% (preferably 15%), so as to change the proportion of water-stable aggregates and bulk density, organic carbon content and heavy metal dissolution ratio in the tailings, and initially form a soil-like matrix suitable for the colonization of pioneer plants; The rhizosphere bacterial liquid of the mining area soil plants is obtained by selecting the rhizosphere soil of the plants around the mining area, mixing the rhizosphere soil with water at a mass ratio of 1:100, filtering, and collecting the supernatant; Step 3. Sow pioneer herbs and inoculate with functional microorganisms.

[0009] 2. Preferably, the in situ soilization method is characterized in that it also includes step 4. 3 to 12 months after planting pioneer herbaceous plants, when the content of water-stable aggregates in the tailings matrix increases to more than 65%, and the total organic carbon and total nitrogen contents are respectively higher than 12 g / kg and 3 g / kg, start planting shrubs and / or trees to construct a biodiversity ecosystem.

[0010] 3. Preferably, the in-situ soil method is characterized in that: in step 1, the exogenous organic matter refers to a mixture of biomass and biochar in a ratio of 1:1.

[0011] 4. Preferably, the in-situ soil method is characterized in that the weight ratio of the added amount of the exogenous organic matter to the tailings of the tailings pond is 5-7%.

[0012] 5. Preferably, in the in-situ soil treatment method, the rhizosphere bacterial solution of the mining area soil plants in step 2 is applied 5 to 7 days after step 1, and the application amount is 15-35 L / m 2 .

[0013] 6. Preferably, in the in-situ soil treatment method, in step 1, a soil metal passivator is further added; the soil metal passivator is selected from one or more of diatomaceous earth, slag silicon fertilizer, silicon-based modified biochar, nano zero-valent iron loaded activated carbon, montmorillonite, and zeolite; and the added amount is 1 to 6 g per kilogram of tailings.

[0014] 7. Preferably, in the in situ soil method, the sowing of pioneer herbaceous plants in step 3 refers to sowing one or more of ryegrass, double paspalum, alfalfa, and white clover; wherein the sowing ratio of ryegrass, broadleaf cattail, white clover, and alfalfa is 0.10-0.15: 0.10-0.15: 0.35-0.40: 0.35-0.40 according to seed mass, and the sowing amount is 30-50g / m 2 .

[0015] Pioneer Herbaceous Plants uses fast-growing ryegrass and broad-leaved cattails that are tolerant to high salinity and heavy metal pollution, combined with white clover and alfalfa that are tolerant to barrenness and have nitrogen-fixing capabilities. They can promote the rapid formation of soil-like matrices, fix heavy metals, and reduce heavy metal dissolution.

[0016] 8. Preferably, in the in-situ soil method, the change in the proportion of water-stable aggregates, bulk density and organic carbon content in the tailings in step 1 means that the content of water-stable aggregates is not less than 35%, 40%, 45% or 50%, and the soil bulk density is not higher than 1.7 g / cm 3 Below, the organic carbon content is above 2-3.5%.

[0017] 9. Preferably, in the in situ soil method, the inoculation of functional microorganisms in step 3 refers to inoculation of Pseudomonas aeruginosa and / or arbuscular mycorrhizal fungi.

[0018] 10. Preferably, the in-situ soilification method is characterized in that: In step 1, after adding exogenous organic matter and mixing to obtain the tailings matrix, the tailings matrix is ​​ridged at intervals of 1.8 meters, leaving ridges with a width of 0.5 meters and a depth of 0.4 meters; 5-10 days after sowing the pioneer herbaceous plants in step 3, the surface of the tailings matrix is ​​covered with a sunscreen net, and there is no need to uncover the sunscreen net in the later stage of plant growth; and the ridge and canal water conservation strategy is used to maintain the environment for plant growth and regulate the acid production in the early stage of tailings discharge.

[0019] 11. Application of any of the above-mentioned in-situ soilification methods in mine environmental remediation.

[0020] Definition of terms: The "biomass" referred to in the present invention refers to processed agricultural, forestry and animal husbandry organic wastes, such as straw, leaves, sawdust, bagasse, rice bran and wheat bran; the processing refers to one or more of crushing, stockpiling and fermentation.

[0021] The "biochar" referred to in the present invention is a substance formed by incomplete combustion of natural organic fuels under low oxygen or anoxic conditions, wherein natural organic fuels include fallen leaves, abandoned trees, straw, urban organic waste, livestock feces, etc. It has a wide range of sources, mature technology, and is easy to obtain. "Water-stable aggregates" refer to the aggregates that do not disperse immediately after the soil structure is immersed in water and keep the soil structure shape intact. It is a structural unit in the soil with different sizes and shapes, different porosity, mechanical stability and water stability. The structural unit with a particle size of >0.25mm is usually called a large aggregate. Generally, the wet screening method is used to obtain the proportion of water-stable aggregates of different particle sizes in the soil.

[0022] The technical concept of the present invention: In view of the guiding principles of resource utilization, volume reduction, and harmless treatment of solid waste, the adoption of ecological restoration measures for the management of tailings ponds is the most sustainable strategy that conforms to the above principles. In theory, ecological restoration of tailings ponds can effectively reduce the concentration of heavy metals in the tailings area and significantly improve the quality of tailings sand soil; however, the inventors found in their research that the high concentration of heavy metals and the lack of inherent nutrients in the tailings are not conducive to plant growth. In response to this problem, the inventors speculate that the application of the role of microbial communities will be a key link in solving this problem. Microorganisms not only help improve the nutrient cycle of tailings and increase the survival rate of plants, but also play a key role in carbon and nitrogen fixation; providing a new perspective for the ecological restoration of tailings areas.

[0023] In the prior art, there is a relative lack of research on tailings in production and use, especially in the entire process of "storage-weathering-remediation" of lead-zinc tailings ponds, the dynamic characteristics of soil microbial community succession and the restoration mechanism promoted by microorganisms are still unclear. In the study, the inventors found that the vegetation reconstruction of retired tailings is often accompanied by an increase in the abundance of carbon-fixing and nitrogen-fixing related microorganisms. Through the natural succession of rhizosphere microorganisms, the retired tailings area has established a microbial community that is conducive to plant growth; the inventors speculate that these microbial communities can be used to promote plant growth in the tailings area in production and use. Based on this speculation, an important attempt in the in-situ soilization method of tailings of the present invention is to use the rhizosphere bacterial liquid (rich in microbial communities and root secretions) of plants around the mining area, and add it to the mineral sand of the tailings pond in production and use to be treated in situ to promote the soilization of the tailings sand and the growth of plants.

[0024] In addition, the in-situ soil formation method of the present invention has been found to rapidly promote the formation of water-stable aggregates in the ore sand by adding a small amount of exogenous organic matter in a specific proportion, especially a mixture of biomass and biochar, which can effectively drive the tailings to form a new technical soil with an ideal proportion. The data of the embodiment of this case show that the content of water-stable aggregates increased to more than 50% only at the end of stage 1.

[0025] In summary, the technical solution of the tailings in-situ soilification method provided by the present invention includes the following three steps: 1. Use exogenous organic matter (biomass) combined with biochar to promote the development of water-stable aggregates, nutrient accumulation, heavy metal fixation, and acid-base regulation in tailings, so that the soil-like matrix obtained in the early stage is suitable for the colonization of pioneer plants; 2. Stimulate the development of functional microorganisms in tailings by adding rhizosphere soil bacterial solution (rich in microbial communities and root secretions); 3. Use pioneer plants suitable for tailings soil matrix at different development stages and add exogenous plant root symbiotic bacteria to support Pioneer plant colonization.

[0026] Initial plant biomass and biochar are combined to improve tailings, and plant fast-growing, nitrogen-fixing herbaceous plants that are tolerant to salinity and barrenness. Plants; transplant trees and shrubs six months to one year after planting to improve biodiversity and restore ecosystem stability.

[0027] The experimental data of the present invention show that the ecological restoration of tailings by "in-situ matrix improvement + direct planting of vegetation" Strategy: By adding a low amount of external modifiers (exogenous organic matter + rhizosphere bacterial liquid), the physical structure and fertility conditions of the fine-grained tailings matrix can be effectively improved in a short period of time (30-50 days), making it suitable for the colonization of pioneer herbaceous plants. Within 6-12 months, the tailings pond can achieve environmental conditions suitable for long-term plant growth, making the vegetation in the tailings pond evergreen all year round and the heavy metals stable and solidified without migration, effectively controlling soil erosion and environmental pollution of tailings; The soil treatment method provided by the present invention has been widely promoted and applied in some mine tailings ponds in production and use (e.g., Lead and zinc tail), and achieved good ecological restoration results, with local results Figure 2~3 . BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A diagram of the root growth of sown plants during the application of the in-situ soilification method of the present invention; Figure 2 Field photos of the restoration effect of the in-situ soil treatment method of the present invention; Figure 3 A magnified photograph of the on-site details of the restoration effect of the in-situ soilization method of the present invention. DETAILED DESCRIPTION

[0029] The present invention is exemplified below in conjunction with specific embodiments, but should not be construed as limiting the present invention.

[0030] Example 1: In-situ soil treatment of vanadium-titanium magnetite tailings Tailings background analysis: Vanadium-titanium magnetite tailings, like most tailings, have the same problems of fine particles, large volume and poor quality. In addition, the main minerals of vanadium-titanium magnetite tailings include: ilmenite, titanomagnetite, apatite, etc., as well as gangue minerals such as pyroxene-titanium pyroxene, olivine, feldspar, mica, and amphibole. Gangue minerals are consistent with local soil parent materials, except that the titanium-containing minerals will flow to the surrounding soil, water and other environmental media during the accelerated weathering process of the tailings exposed to the air, and then enter the organism.

[0031] According to the results of elemental analysis, the mineral element composition of a vanadium-titanium magnetite tailings is as follows: iron (TFe): 15.3%, titanium (TiO2): 10.9%, sulfur (S): 0.28%, phosphorus (P2O5): 1.01%, silicon (SiO2): 35.6%, aluminum (Al2O3): 8.65%, calcium (CaO): 12.0%, magnesium (MgO): 8.14%, potassium (K2O): 0.74%. Sodium (Na2O): content is 1.62%, manganese (MnO): content is 0.27%, vanadium (V2O5): content is 0.10%, chromium (Cr2O3): content is 358ppm (i.e. 0.0358%), scandium (Sc2O3): content is 40.4ppm (i.e. 0.0404%). It can be seen that the vanadium-titanium magnetite tailings contain mineral elements required for plant growth, and trace amounts of chromium have a low risk to the restoration of non-agricultural land, but the rich phosphorus in the form of apatite is difficult to be used by plants. Therefore, the most important thing for the development of vanadium-titanium magnetite tailings soil matrix is ​​to form a porous structure similar to soil (water-stable aggregates) to overcome the problem that the mineral elements in the matrix are difficult to be absorbed by plants.

[0032] The present invention carries out the application test of the present invention in the mining area.

[0033] The specific implementation steps are as follows: (1) Stage 1: Remediation of exogenous organic matter In the tailings pond area, the tailings are leveled and the surface 40 cm of tailings are plowed and loosened to facilitate the flow, sedimentation and mud Water separation and drainage, ventilation; in each treatment, add exogenous organic matter to the tailings at a weight ratio of 3%, mix evenly to obtain the tailings matrix, and then ridge every 1.8 meters, leaving a ridge ditch with a width of 0.5 meters and a depth of 0.4 meters (see Figure 2~Figure 3 ); watering during this period to maintain the moisture content of the tailings matrix on the ridge at 15% w / w; After 5-7 days, add rhizosphere soil bacterial solution when watering (apply 15-35L per square meter of ridge area); after 30 days of in situ cultivation, take samples for testing. The results are shown in the data of treatments 1 and 2 in Table 1; The rhizosphere soil bacterial solution is obtained by collecting the plant rhizosphere soil around the mining area, mixing the plant rhizosphere soil with water at a mass ratio of 1:100, filtering, and collecting the supernatant to obtain the rhizosphere soil bacterial solution; Alfalfa biomass: Derived from local alfalfa hay, crushed to 2-5mm.

[0034] Bagasse biomass: It comes from the waste left over from sugar production in sugar factories. After drying, it is mixed evenly and crushed to 2-5mm.

[0035] (2) Stage 2: Establishment of pioneer herbaceous plants The cultured tailings matrix is ​​naturally air-dried and then mixed loosely and evenly. Then, during the transition period between spring and summer, when there is abundant rainfall and the temperature is around 22~28℃, the seeds of double-spike paspalum are sown. Water the seeds immediately after sowing to maintain moist conditions that are conducive to seed germination.

[0036] After germination, the germination rate was recorded. Six months after planting, the physical and chemical properties of the tailings and the plants were sampled and tested. The results are shown in Table 1 for treatments 3 and 4. The plant root development test is shown in Figure 1 , it can be seen that in the soil-improved tailings matrix, the root systems of pioneer plants are well established and developed.

[0037] (3) Stage 3: Planting of woody trees and shrubs Half a year later, holes were dug in areas where Paspalum distachyon was sparse to transplant Acacia macrophylla seedlings and inoculate with arbuscular mycorrhizal fungi. Half a year after planting, some tailings samples and plant samples were harvested for testing; the results are shown in Table 1 for data of treatments 5 and 6.

[0038] For the plant samples taken during the above-mentioned restoration process, the plant height, dry matter weight, mineral element content and distribution in different tissues were measured; for the tailings samples taken, the development of the physical structure of the matrix (water-stable aggregate content), fertility development (organic carbon, nitrogen, available phosphorus, and available potassium content), and environmental stress (pH, electrical conductivity EC, weak acid extractable Cr content) were evaluated.

[0039] The method for determining water-stable aggregates is as follows, and the other determinations are conventional methods in the art.

[0040] Determination method: Use a wet sieving instrument and a series of sieves with different apertures to take a certain amount of dry soil to be tested, and wet-sieve it for one minute under simulated rainfall and certain vibration conditions. Unstable aggregates will be broken up and pass through the sieve, while water-stable aggregates will remain on the sieve. Collect the water-stable aggregates on the sieve, dry and weigh them, and compare them with the initial sampled soil weight to obtain the proportion of water-stable aggregates with different particle sizes.

[0041] The changes in the physical and chemical properties of the tailings are shown in Table 1, and the growth of Paspalum distachyon inoculated with or without arbuscular mycorrhizal fungi in tailings improved with different biomass is shown in Table 2; The actual photos of the application effect of the tailings in-situ soil restoration of the present invention are as follows: Figure 2~Figure 3 Example.

[0042] Table 1. Physicochemical properties of tailings during the three-stage restoration process (biomass-pioneer herbaceous plant colonization-woody tree and shrub plant colonization)

[0043] The above data show that after adding exogenous plant biomass, about 44% water-stable aggregates were formed in the tailings, and herbaceous plant colonization increased the content of water-stable aggregates to about 47%; after woody plant colonization, the content of water-stable aggregates in the matrix further increased to 61.8%; compared with plant biomass colonization, herbaceous plant colonization increased the organic carbon and nitrogen content in the tailings and reduced the weakly acid extractable Cr content.

[0044] Comprehensive data in Table 1, comparing the data of treatments 4 and 6 and the data of treatments 3 and 5, it can be seen that after the planting of woody plants, the changes in various indicators are further enhanced, proving that the joint restoration model of plant biomass improvement + pioneer herbaceous plant planting + tree and shrub plants can rapidly promote the in-situ soil development of vanadium-titanium magnetite tailings; After further follow-up testing, the percentage of water-stable large aggregates further increased to 65-75% after the roots of woody plants were established.

[0045] Table 2. AM fungal infection rate in the roots of Acacia sempervirens and plant biomass per hole

[0046] The data in Table 2 show that after inoculation with rhizosphere mycorrhizal fungi, the aboveground and underground biomass of the colonized plants increased significantly.

[0047] Example 2: In-situ soil treatment of lead-zinc mine tailings matrix Background of tailings to be treated: Lead-zinc tailings are a typical type of metal mine tailings containing sulfide minerals. The main mineral types include gangue minerals (such as quartz, calcite, dolomite / ferrodolomite, mica, etc.) and metal sulfides (pyrite, galena, sphalerite, arsenopyrite, etc.). These sulfides are the products of reducing conditions. Therefore, as the tailings are exposed to the air environment, these sulfide metal minerals are gradually oxidized, resulting in acid mine wastewater and the dissolution of heavy metal ions. Therefore, an important limiting issue facing the ecological restoration of sulfide metal mine tailings is the gradual acidification of tailings and the release of heavy metals. In addition, like the limiting factors for the development of most tailings soil matrices, the development of lead-zinc tailings soil matrices also needs to overcome the problems of barrenness and compaction of tailings. Therefore, organic remediation, such as adding exogenous plant biomass, biochar, compost, etc., is also a commonly used remediation measure, which often aggravates the oxidation and reduction of minerals in sulfide metal tailings, dissolution and precipitation, and thus affects the dissolution and fixation, adsorption and analysis of heavy metal ions. Scientifically regulating the proportion of materials that can promote the dissolution and fixation of heavy metals in ecological restoration, and balancing the physical structure and fertility of the tailings soil matrix required to support plant growth as well as the environmental stresses it faces are crucial for stable and sustainable ecological restoration.

[0048] The invention conducts an application test of the invention in the mining area, using plant biomass and biochar to jointly stimulate the development of lead-zinc tailings soil matrix and heavy metal stabilization and remediation strategies, specifically including the following steps: (1) Stage 1: Remediation of exogenous organic matter The surface 40cm of the Pb-Zn tailings reservoir area was leveled, plowed and loosened to facilitate the flow, sedimentation, mud-water separation and drainage of the tailings and ventilation; the treatment was set up according to Table 3, exogenous organic matter was added to the tailings according to the weight ratio, and the tailings matrix was obtained by mixing evenly, and then ridges were formed every 1.8 meters, leaving ridge furrows with a width of 0.5 meters and a depth of 0.4 meters; watering was performed during the period to maintain the moisture content of the tailings matrix on the ridges at 15% w / w; After 5-7 days, add rhizosphere soil bacterial solution to each treatment when watering (15-35L of rhizosphere soil bacterial solution per square meter); maintain the moisture content at 15% and continue to culture for 30 days, and then take samples for testing.

[0049] After the completion of stage 1, the water-stable aggregate content, total organic carbon, total nitrogen, available phosphorus, and the dissolution amounts of the main heavy metals Pb, Zn, and Cd in the tailings matrix were determined, as shown in Table 3.

[0050] Table 3 Physical and chemical properties of lead-zinc tailings after adding different proportions of exogenous organic matter

[0051] Note: Biomass refers to alfalfa biomass, and biochar refers to alfalfa biochar. The alfalfa biochar used is obtained by burning alfalfa hay at 500°C.

[0052] The above test results show that as the proportion of exogenous organic matter (biomass + biochar) added increases from 3%, 6% to 10%, the dissolution of heavy metals increases, and the dissolution of heavy metals in the scheme with the addition of biochar is significantly reduced; it is also found that the addition of 3% exogenous organic matter (biomass + biochar) can stimulate the tailings to form a water-stable aggregate content of more than 35%, and the organic carbon and total nitrogen contents exceed 1.5% and 8 g / kg respectively, but the effective phosphorus content is lower in the scheme with the addition of 3% biochar; When exogenous organic matter (biomass and / or biochar) is added to 6%, it can effectively drive the tailings to form an ideal proportion of technological new soil (Technosol); at the same time, it was found that the scheme of adding biomass and biochar in a 1:1 ratio can effectively drive the tailings to form an ideal proportion of technological new soil physical structure (water-stable aggregate content reaches 56%), fertility (organic carbon, 3.8%, total nitrogen 18g / kg, available phosphorus 18g / kg) and heavy metal dissolution balance.

[0053] Therefore, the present invention proposes to add exogenous organic matter according to 3% biomass + 3% biochar to stimulate the development of tailings technology new soil (Technosol).

[0054] (2) Phase II: Colonization of pioneer herbs and functional microorganisms In Technosol, a heavy metal-tolerant herb, Paspalum bicolor, was planted and functional bacteria were inoculated in Technosol after adding 3% biomass and 3% biochar. The specific treatments were as follows: 'P' stands for planting double paspalum grass; ‘P+B’ represents planting double paspalum grass and inoculating with P. aeruginosa ; ‘P+A’ represents planting with double paspalum and inoculating with arbuscular mycorrhizal fungi; 'P+B+A' represents planting of double paspalum and inoculating with Pseudomonas aeruginosa and arbuscular mycorrhizal fungi After three months of growth, plant biomass and heavy metal contents in plant roots and aboveground parts were measured (see Table 4).

[0055] Pioneer herbaceous plants begin to germinate 5-10 days after sowing and need to be covered with a sun-proof net, which does not need to be uncovered after the plants grow. In addition, the ridge and canal water conservation strategy is used to maintain the environment for plant growth and regulate the acid production in the early stage of tailings discharge. The ridge and canal width is 30cm, and the width between two ridges is 60-80cm.

[0056] Table 4 Growth of Paspalum bicolor inoculated with Pseudomonas aeruginosa and / or arbuscular mycorrhizal fungi in lead-zinc tailings remediated with 3% alfalfa biomass and 3% alfalfa biochar

[0057] The measurement results showed that the simultaneous inoculation of arbuscular mycorrhizal fungi and Pseudomonas aeruginosa not only increased the root biomass of the plants, but also reduced the Pb and Zn contents in the aboveground parts of the barnyardgrass; at the same time, the accumulated Pb and Zn contents in the roots increased significantly after inoculation of arbuscular mycorrhizal fungi and Pseudomonas aeruginosa, indicating that the inoculation of functional bacteria can hinder the transport of heavy metals from the roots to the aboveground parts to alleviate heavy metal stress.

[0058] Example 3 Development of lead-zinc mine tailings soil matrix The background of the tailings to be treated and the plant colonization management measures are the same as those in Example 2.

[0059] The specific processing steps are as follows: (1) Stage 1: Exogenous organic matter restoration: The surface 40cm of the Pb-Zn tailings reservoir area is leveled, plowed and loosened to facilitate the flow, sedimentation and muddy water of the tailings. Separation and drainage, ventilation; according to the treatment set in Table 5, add exogenous organic matter and silicon-based passivating agent to the tailings according to the weight ratio, mix evenly to obtain tailings matrix, and then ridge every 1.8 meters, leaving a ridge ditch with a width of 0.5 meters and a depth of 0.4 meters; water during the period to maintain the moisture content of the tailings matrix on the ridge at 15% w / w; After 5 to 7 days, add rhizosphere soil bacterial solution to each treatment when watering (15-35L of rhizosphere soil bacterial solution per square meter), maintain 15% moisture content for 30 days, and take samples for testing.

[0060] (2) Stage 2: Establishment of pioneer herbaceous plants The pioneer herbaceous plant Paspalum bicolor was planted, and a control group without plants was set up. After half a year of cultivation, the plant growth and the development of the tailings soil matrix were monitored. See Table 6.

[0061] Table 5 Experimental design

[0062] Note: The organic matter is alfalfa biomass; the silicon-based passivator adopts the multi-effect environmentally friendly silicon-based soil heavy metal passivator recorded in the inventor's previous patent CN109456774B.

[0063] Table 6 Plant growth and tailings soil matrix development six months after pioneer herbaceous plants were planted

[0064] The results showed that the addition of exogenous organic matter increased the organic carbon and nitrogen content of the tailings and increased the water-stable aggregate content of the matrix, indicating that the addition of exogenous organic matter was beneficial to the improvement of the physical structure and fertility of the tailings and promoted the development of tailings soil. However, the addition of exogenous organic matter also increased the content of weakly acid-extractable heavy metals in the tailings. Adding a silicon-based passivator on the basis of adding exogenous organic matter not only maintained the physical structure and fertility of the matrix, but also reduced the content of weakly acid-extractable heavy metals in the matrix, which was more conducive to plant colonization.

Claims

1. An in-situ soil treatment method for tailings from an in-production tailings pond, characterized in that: The following steps are involved: Step 1. In situ, the tailings of the tailings pond of the mine in production and use are leveled, the surface 40 cm of the tailings are ploughed and loosened, and exogenous organic matter is added to mix the tailings and the exogenous organic matter evenly to obtain a tailings matrix, wherein the exogenous organic matter refers to a mixture of biomass and biochar in a ratio of 1-2:1-2, and the weight ratio of the added amount of the exogenous organic matter to the tailings of the tailings pond is 3-8%; then ridges are formed at intervals of 1.8-2 meters, leaving ridges with a width of 0.5-0.8 meters and a depth of 0.4-0.6 meters; Step 2. 5 to 7 days after step 1, spray the rhizosphere bacteria solution of the mining area soil plants in the tailings matrix, the application amount is 15-35L per square meter of the tailings matrix, and culture in situ for 20 to 40 days, during which the water content is ensured to be 12 to 18%, so as to improve the proportion of water-stable aggregates and bulk density, organic carbon content and heavy metal dissolution ratio in the tailings, and initially form a soil-like matrix suitable for the colonization of pioneer plants; The rhizosphere bacterial liquid of the mining area soil plants is obtained by selecting the rhizosphere soil of the plants around the mining area, mixing the rhizosphere soil with water at a mass ratio of 1:100, filtering, and collecting the supernatant; Step 3. Sow pioneer herbs and inoculate with functional microorganisms.

2. The in-situ soilification method according to claim 1, characterized in that: It also includes step 4: 3 to 12 months after planting pioneer herbs, when the water-stable aggregate content in the tailings matrix increases to more than 65%, and the total organic carbon and total nitrogen contents are higher than 12g / kg and 3g / kg respectively, shrubs and / or trees are planted to build a biodiversity ecosystem.

3. The in-situ soilification method according to claim 1, characterized in that: In step 1, the exogenous organic matter refers to a mixture of biomass and biochar in a ratio of 1:

1.

4. The in-situ soilification method according to claim 1, characterized in that: The weight ratio of the added amount of the exogenous organic matter to the tailings in the tailings pond is 5-7%.

5. The in-situ soilification method according to any one of claims 1 to 4, characterized in that: In step 1, a soil metal passivator is also added; the soil metal passivator is selected from one or more of diatomaceous earth, slag silicon fertilizer, silicon-based modified biochar, nano zero-valent iron loaded activated carbon, montmorillonite, and zeolite; the added amount is 1 to 6 g per kilogram of tailings.

6. The in-situ soilification method according to any one of claims 1 to 4, characterized in that: The sowing of pioneer herbaceous plants in step 3 refers to sowing ryegrass, broad-leaved cattail, white clover and alfalfa; the sowing ratio of ryegrass, broad-leaved cattail, white clover and alfalfa is 0.10-0.15: 0.10-0.15: 0.35-0.40: 0.35-0.40 according to seed mass, and the sowing amount is 30-50 g / m 2 .

7. The in-situ soilification method according to any one of claims 1 to 4, characterized in that: The change in the proportion of water-stable aggregates, bulk density and organic carbon content in the tailings in step 1 means that the content of water-stable aggregates is not less than 35%, 40%, 45% or 50%, and the bulk density of soil is not higher than 1.7 g / cm 3 , the organic carbon content is not less than 2% or not less than 3.5%.

8. The in-situ soilification method according to any one of claims 1 to 4, characterized in that: The inoculation of functional microorganisms in step 3 refers to inoculation of Pseudomonas aeruginosa and / or arbuscular mycorrhizal fungi.

9. The in-situ soilification method according to any one of claims 1 to 4, characterized in that: In step 1, after adding exogenous organic matter and mixing to obtain the tailings matrix, the tailings matrix is ​​ridged at intervals of 1.8 meters, leaving ridges with a width of 0.5 meters and a depth of 0.4 meters; 5-10 days after sowing the pioneer herbaceous plants in step 3, the surface of the tailings matrix is ​​covered with a sunscreen net, and there is no need to uncover the sunscreen net in the later stage of plant growth; and the ridge and canal water conservation strategy is used to maintain the environment for plant growth and regulate the acid production in the early stage of tailings discharge.

10. Use of the in-situ soilification method according to any one of claims 1 to 9 in environmental remediation of mine tailings ponds.

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