Method for repairing acid mine by using domestic waste landfill site to screen humus soil

Abstract

This invention discloses a method for remediating acidic mines using humus extracted from municipal solid waste landfills, relating to the technical field of ecological restoration of acidic mine waste sites. The method includes the following steps: excavating municipal solid waste landfills to obtain aged waste, crushing and screening it to obtain screened humus; analyzing the composition of organic matter, nutrients, and heavy metals in the screened humus; harmless screening; nutrient adjustment; soil improvement; vegetation restoration; and monitoring and evaluation of the remediation effect. This method not only reduces the cost and improves the efficiency of acidic mine remediation but also promotes the restoration of the ecological function of the mine waste site through vegetation restoration, while effectively improving the resource reuse efficiency of the screened humus. This invention is applicable to the remediation of different types of acidic mine waste sites, such as pyrite, sulfur-containing metal ores, and ion-adsorption rare earth ores, contributing to the achievement of sustainable development goals.

Description

Technical Field

[0001] This invention relates to the technical field of ecological restoration of acidic mine waste sites, and in particular to a method for restoring acidic mines by screening humus soil from municipal solid waste landfills. Background Technology

[0002] Against the backdrop of rapid urbanization, the issue of urban solid waste disposal has become increasingly prominent. Currently, over 70% of urban waste in my country relies on sanitary landfills for treatment. While this has alleviated the pressure on waste management in the short term, the continuous increase in waste volume has led to increasingly strained landfill space. How to efficiently utilize landfill space has become an urgent problem to solve. Furthermore, although the screened humus produced from landfills contains organic matter and nutrients, it also contains harmful substances such as heavy metals, limiting its direct use in land application.

[0003] In the mining sector, the ecological restoration of abandoned sites is equally challenging. Traditional restoration methods are not only costly but also not always effective. Ecological environmental protection and restoration of mining areas are crucial aspects of mineral resource development. Faced with problems such as high acidity, poor soil quality, and heavy metal pollution in acidic mining abandoned sites, soil improvement typically requires a combination of methods, including organic amendments, minerals, and biochar. These methods often require substantial financial investment, and the effectiveness of restoration remains uncertain. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for remediating acidic mines using humus soil screened from municipal solid waste landfills. This method enables the resource utilization of screened humus soil, effectively increases the pH of acidic mine soil, controls the risk of heavy metal pollution, and promotes the ecological restoration of abandoned acidic mine sites. The method aims to transform screened humus soil from municipal solid waste landfills into resources for acidic mine remediation, thereby achieving the resource utilization of solid waste and the ecological restoration of abandoned acidic mine sites.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a method for remediating acidic mines by screening humus from municipal solid waste landfills, comprising the following steps:

[0007] (1) Excavate the domestic waste landfill to obtain old waste, crush and screen it to obtain screened humus;

[0008] (2) Analyze the heavy metals in the screened humus. If it meets the Class III standard of "LY / T 1970—2011-Organic substrate for greening", then proceed to step (3). If it does not meet the Class III standard of "LY / T 1970—2011-Organic substrate for greening", then carry out harmless landfill treatment on the screened humus.

[0009] (3) Analyze the organic matter and nutrients in the sieved humus. If the results of the component analysis meet the improvement substrate standard of "LY / T 1970—2011-Greening Organic Substrate", then proceed to step (4) or (5); if the results do not meet the improvement substrate standard of "LY / T1970—2011-Greening Organic Substrate", then add an amendment. Determine the amount of amendment based on the soil analysis results and the characteristics of the amendment. Adjust the nutrient content of the sieved humus to meet the improvement substrate standard of "LY / T 1970—2011-Greening Organic Substrate", then proceed to step (4) or (5).

[0010] (4) Analyze the site conditions of acid mine wasteland. For acid mine wasteland with gentle slope and soil cover, screened humus soil that meets the improvement substrate standard of "LY / T 1970—2011-Greening Organic Substrate" should be used as organic substrate. Improvement and plowing should be adopted for remediation. The amount of screened humus soil should be determined according to the nutrient analysis results of acid mine soil and the characteristics of screened humus soil. The organic matter and nutrient content in the mixed soil after plowing should meet the Class IV standard of "CJ / T 340—2016-Greening Planting Soil".

[0011] (5) Analyze the site conditions of acid mine wasteland. For acid mine wasteland with steep slopes and no soil layer or thin soil cover, screened humus soil that meets the improvement substrate standard of "LY / T 1970—2011-Greening Organic Substrate" is used as organic substrate. It is mixed with low nutrient soil to dilute the organic substrate and directly covered to repair and form a new soil layer. The new soil layer should meet the Class IV standard of "CJ / T 340—2016-Greening Planting Soil".

[0012] (6) Sow or plant vegetation on the improved soil;

[0013] (7) Finally, the soil remediation effect is monitored and evaluated regularly.

[0014] This invention scientifically processes screened humus from municipal solid waste landfills, making it suitable for soil remediation in acidic mines, thus achieving resource reuse of waste and ecological restoration of abandoned acidic mine sites. This method not only effectively treats screened humus from municipal solid waste landfills but also provides a cost-effective solution for the remediation of abandoned acidic mine sites. Through harmless treatment and nutrient balance adjustment, this invention transforms screened humus into soil material suitable for plant growth, enabling vegetation restoration in abandoned acidic mine sites and promoting ecosystem reconstruction and functional recovery. The implementation of this method is expected to significantly improve soil conditions, vegetation cover, and biodiversity in mining areas, restore the ecological functions of mines, and promote sustainable development in mining regions.

[0015] Preferably, in step (2), the screened humus is pre-dried, crushed, and sieved.

[0016] This invention improves the applicability and effectiveness of soil by air-drying and pulverizing humus soil.

[0017] Preferably, the heavy metals in step (2) include copper, iron, lead, zinc, cadmium, and chromium.

[0018] Preferably, the nutrients in step (3) include at least one of nitrogen, phosphorus, potassium, calcium, and magnesium.

[0019] Preferably, the improver in step (3) includes at least one of phosphate fertilizer, nitrogen fertilizer, potassium fertilizer, organic manure, biochar, crop residue, compost, and green manure.

[0020] In practical applications, the amendment can be a single substance or a mixture of two or three substances. The types and proportions of the mixture need to be determined based on the specific soil conditions of the acidic mine waste site (such as organic matter content, nutrient content, etc.), the composition analysis results of the sieved humus, and the remediation goals.

[0021] When the soil has low organic matter content and lacks inorganic nutrients, applying 0.1-0.5% inorganic fertilizer (based on the dry weight of sieved humus) + 1-10% organic manure can simultaneously increase the organic matter and inorganic nutrient content of the soil.

[0022] When the soil has low organic matter content and it is necessary to improve the soil's water retention and aeration, applying 1-10% organic manure and 1-5% biochar by weight can simultaneously increase the soil's organic matter content and improve its structure.

[0023] When the soil has low organic matter content and it is necessary to improve the soil’s biological activity, applying 1-10% by weight of crop residue + 1-10% by weight of compost can simultaneously improve the soil’s organic matter content and biological activity.

[0024] When the soil has low organic matter content, lacks inorganic nutrients, and needs to improve soil water retention and aeration, applying 0.1-0.5% inorganic fertilizer + 1-10% organic manure + 1-5% biochar by mass can comprehensively increase organic matter content, provide inorganic nutrients, and improve soil structure. The specific compound ratio needs to be confirmed and verified through theoretical calculations, small-scale experiments, and actual working conditions.

[0025] Preferably, the acidic mine site conditions in step (4) or (5) include at least one of the following: topographic conditions, soil physicochemical properties, hydrological conditions, climatic conditions, biological conditions, and human disturbance factors.

[0026] More preferably, the topographical conditions include slope, aspect, and micro-topography.

[0027] More preferably, the soil physicochemical properties include physical properties and chemical properties, the physical properties including texture, structure, moisture, etc., and the chemical properties including pH value, nutrients, salinity, and pollution.

[0028] More preferably, the hydrological conditions include surface water, groundwater, and water quality.

[0029] More preferably, the climatic conditions include sunlight, precipitation, temperature, and wind.

[0030] More preferably, the biological conditions include microorganisms, seed bank, animals, and existing vegetation.

[0031] More preferably, the human interference factors include engineering legacy, pollution sources, and land use history.

[0032] In practical applications, the main considerations are slope, micro-topography, soil physicochemical properties, engineering legacy, and land use history. On steep slopes (>40°) with no soil layer or a thin soil cover, the topsoil should be at least 10cm thick and compacted. On slopes >70°, a galvanized iron mesh should be laid on the surface to stabilize the soil. On gentle slopes (<40°) or in areas with residual soil layers, the proportion of sieved humus added should be adjusted based on the original soil analysis results. The general addition amount (2-10% by weight) should ensure that the 0-10cm soil after tillage and mixing meets the Class IV standard of "CJ / T340—2016-Green Planting Soil".

[0033] Preferably, in step (4), for acidic mine wasteland with gentle slope and soil cover, the screened humus soil that meets the improved matrix standard is mixed with the acidic mine wasteland soil at a mass ratio of (0.02-0.1):1, and then the mixed soil is covered on the surface of the acidic mine wasteland with a thickness of not less than 10cm.

[0034] Preferably, in step (5), for acid mine wasteland with steep slopes and no soil layer or thin soil layer, the screened humus soil that meets the improved matrix standard is mixed with low nutrient soil at a mass ratio of 1:(3-10), and then the mixed soil is covered on the surface of the acid mine wasteland with a thickness of not less than 10cm.

[0035] Preferably, in step (5), when the organic matter content of the screened humus exceeds the upper limit of the standard (80g / kg) of "CJ / T 340-2016-Green Planting Soil", low-nutrient soil is added and mixed according to the mass ratio, and the mixing ratio is screened humus: low-nutrient soil = 1:(3~10).

[0036] Preferably, the low-nutrient soil in step (5) includes at least one of garden soil, sandy soil, clay, and construction waste soil.

[0037] Preferably, in step (6), native and pioneer plant species adapted to the acidic mine wasteland environment are selected for sowing or planting to improve the survival rate and ecological adaptability of the vegetation.

[0038] Native plants refer to plant species that have adapted and grown in the local natural environment for a long time. They have strong ecological adaptability and ecological stability, and are generally identified through field surveys near the restoration area. Pioneer plants are usually those plants that can grow rapidly in harsh environments and have strong tolerance. They can survive in acidic soils and heavy metal pollution environments and improve soil conditions. These include herbaceous plants such as ryegrass, bermudagrass, miscanthus, tall fescue, foxtail grass, and alfalfa; legumes such as Amorpha fruticosa, pigeon pea, and pigweed; Asteraceae plants such as dandelion, zinnia, marigold, and coreopsis; shrubs such as bougainvillea, honeysuckle, and Vaccinium bracteatum; and trees such as Pinus massoniana, Cunninghamia lanceolata, and Sapium sebiferum.

[0039] Preferably, the monitoring indicators in step (7) include soil quality parameters, vegetation coverage, plant growth status and heavy metal content in the soil, which is conducive to comprehensively evaluating the remediation effect, ensuring the continuity and effectiveness of the remediation work, adjusting the remediation plan in a timely manner, and improving the remediation success rate.

[0040] Preferably, the qualified indicators for monitoring include: soil pH > 6, organic matter content > 1.5%, soil heavy metal available content reduced by 70%, vegetation coverage > 90%, and plant species > 10.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] (1) This invention provides an innovative collaborative remediation method for acidic mine waste sites. Through a systematic solution of "waste-resource utilization-ecological restoration," it demonstrates significant advantages in resource reuse, cost savings, and environmental improvement. This method establishes a three-step treatment standard for sieving humus soil: "heavy metal detection-harmless screening-nutrient adjustment." It develops differentiated construction processes for different site conditions in various mining areas and constructs an optimized configuration system of "sieving humus soil-suitable plants." This effectively solves the problem of resource utilization of excavated materials from municipal solid waste landfills, improves the resource utilization rate of excavated materials, reduces environmental pollution, achieves sustainable waste management, and lowers treatment costs, providing a new solution for environmental protection and resource recycling. Simultaneously, it addresses existing problems in mine waste sites such as soil infertility and heavy metal pollution, which hinder vegetation growth and result in poor ecological restoration. Compared with traditional technologies, this invention shortens the remediation cycle from 3-5 years to 1-2 years and reduces costs to 60-150 yuan / m². 2 The vegetation coverage can reach over 85%.

[0043] (2) The technological breakthroughs of this invention are reflected in multiple dimensions: it not only improves the resource reuse efficiency of screened humus soil, reduces the cost of acid mine remediation, and improves remediation efficiency, but also promotes the ecological function reconstruction and restoration of mine waste sites through vegetation restoration. This technology is applicable to the remediation of different types of acid mine waste sites, such as pyrite, sulfur-containing metal mines, and ion-adsorption rare earth mines, including open-pit mines, spoil heaps, and tailings ponds, and has achieved significant results in heavy metal control, sustainable waste management, and cost reduction, providing a practical solution for achieving the sustainable development goals of environmental protection and resource recycling. Attached Figure Description

[0044] Figure 1 This is a diagram showing the plant growth in repaired areas A and B after repair in Embodiment 1 of the present invention.

[0045] Figure 2 This is an image of the alien species that has evolved after succession in Embodiment 1 of the present invention.

[0046] Figure 3 This is a diagram showing the plant growth in repaired areas C and D after repair in Embodiment 2 of the present invention.

[0047] Figure 4 This is an image of the local species after succession in Embodiment 2 of the present invention.

[0048] Figure 5 This is a diagram showing the plant growth in repaired areas E and F after repair in Embodiment 3 of the present invention.

[0049] Figure 6 Image of the species after succession in Example 3 of the present invention.

[0050] Figure 7 A diagram showing the growth of the repaired plant in Comparative Example 1 of this invention.

[0051] Figure 8 A diagram showing the growth of the repaired plant in Comparative Example 2 of this invention.

[0052] Figure 9 A diagram showing the growth of the repaired plant in Comparative Example 3 of this invention.

[0053] Figure 10 The diagram shows the growth of the repaired plant in Comparative Example 4 of this invention.

[0054] Figure 11 The diagram shows the plant growth after repair in Comparative Example 5 of this invention.

[0055] Figure 12 A diagram showing the growth of the repaired plant in Comparative Example 6 of this invention. Detailed Implementation

[0056] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments, but the scope of protection and implementation of the present invention are not limited thereto.

[0057] Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0058] Example 1

[0059] The restoration site in this embodiment is a steep slope of a spoil heap in a pyrite mine in Guangdong Province. This spoil heap is characterized by strong acidity, severe heavy metal pollution, lack of soil cover, extreme nutrient deficiency, complete ecological degradation, and steep slope.

[0060] The experiment designed a remediation area, designated Remediation Area A, which was directly covered with a mixture of screened humus from a municipal solid waste landfill and garden soil in a 1:4 mass ratio. Simultaneously, a remediation area, designated Remediation Area B, was established, covered with an organic amendment (organic manure) mixed with garden soil in a 1:4 mass ratio. The aim was to investigate the effects of screened humus from a municipal solid waste landfill as a soil amendment on the soil's physicochemical properties and biodiversity in a pyrite tailings dump, evaluate the remediation effectiveness of this method, and compare it with the remediation effect of organic fertilizer.

[0061] A method for remediating acidic mines by screening humus from municipal solid waste landfills includes the following steps:

[0062] (1) Excavation of aged waste from a municipal solid waste landfill in Guangdong Province. After more than ten years of stable mineralization, the landfill can be preliminarily sorted by a screening machine to obtain humus soil with high nutrient content and rich microorganisms. The particle size of the humus soil after screening is less than 2 mm. Organic manure was purchased from a farmer near the spoil heap of a pyrite mine in Guangdong Province.

[0063] (2) The organic matter content, total nutrients (nitrogen, phosphorus, potassium) and heavy metal content in the screened humus and organic manure in step (1) were analyzed in detail using laboratory analysis methods. As shown in Table 1, the component analysis results show that the organic matter content, total nutrients (nitrogen, phosphorus, potassium) and heavy metal content in the screened humus and organic manure all meet the standard of "LY / T 1970—2011-Organic substrate for greening".

[0064] (3) The sieved humus collected in step (1) is air-dried and pulverized for pretreatment, and then mixed with garden soil at a mass ratio of 1:4 to obtain sieved humus-improved soil. This soil is then mechanically sieved using a sieve machine. The particle size of the sieved humus-improved soil after sieving is less than 2 mm to ensure uniform soil quality. The organic amendment purchased in step (1) is mixed with garden soil at a mass ratio of 1:4 to obtain organic-improved soil, which is then mechanically sieved using a sieve machine. The particle size of the organic-improved soil after sieving is less than 2 mm to ensure uniform soil quality.

[0065] (4) Laboratory analysis methods were used to conduct a detailed analysis of the organic matter content, nutrients (such as nitrogen, phosphorus, and potassium), and heavy metal content in the pretreated sieved humus-improved soil and organic-improved soil from step (3) to assess their suitability for plant growth and potential risks. As shown in Table 2, the component content of the sieved humus-improved soil and organic-improved soil both met the standard of "CJ / T340—2016-Green Planting Soil".

[0066] (5) An investigation and analysis of the organic matter, nutrient, and heavy metal content in a spoil heap of a pyrite mine in Guangdong Province was conducted. This spoil heap is characterized by strong acidity, severe heavy metal pollution, lack of soil cover, extreme nutrient deficiency, complete ecological degradation, and steep slope. Considering factors such as minimizing slope stability, ease of construction, and long-term restoration, direct soil covering was selected for remediation. The treated, screened humus-modified soil and organic-modified soil were then mixed at a concentration of 110-120 kg / m³. 2 The soil was directly applied to the experimental plots of the mine spoil heap to be remediated, forming a new soil layer. The thickness of the covering was determined to be 10-15 cm based on the soil improvement needs and vegetation growth characteristics.

[0067] (6) Apply seeds of 10 kinds of mixed plants, such as native plants and pioneer plants, such as grass, legume, and aster, to the soil after covering in step (5).

[0068] (7) Finally, the vegetation growth status of the improved restoration areas A and B in step (6) is monitored regularly, and 0-10cm mixed soil samples are collected using the five-point method to determine soil quality, heavy metal content and other indicators, and to evaluate the restoration effect and restoration cost, so as to ensure that the expected ecological restoration goal is achieved.

[0069] Table 1. Results of pH, nutrient and heavy metal content in sieved humus and organic manure.

[0070]

[0071]

[0072] Table 2. Results of pH, nutrient and heavy metal content in sieved humus-modified soil and organic-modified soil.

[0073]

[0074] Table 3. Results of soil physicochemical properties test 6 months after remediation

[0075]

[0076] As shown in Table 3, comparing remediation areas A and B, the soil pH was effectively regulated after remediation, the soil acid-base balance was improved, and suitable conditions were created for plant growth. The organic matter content and nutrient levels of the remediated soil were significantly improved, enhancing soil fertility. This not only provided necessary nutrition for plants but also helped improve soil water retention and aeration, thereby promoting plant growth and the health of the soil ecosystem. The available heavy metals were significantly reduced after remediation, reducing potential harm to plants and the environment.

[0077] like Figure 1As shown, comparing restoration areas A and B, one month after restoration, the dominant species was the pioneer plant ryegrass, with occasional rapeseed flowers and sown plants such as clover, goosegrass, and pigweed. Six months after restoration, the coverage exceeded 95%, with the dominant species being the previously sown goosegrass and pigweed. Figure 2 As shown, after six months of natural succession, invasive species such as black nightshade and saltwort wood appeared. In the restoration process, the initial planting of pioneer plants and native plants can quickly cover the soil surface, reduce erosion, and gradually restore ecosystem functions; in the later stages, species diversity and richness gradually increase, and the ecosystem develops towards a more stable and healthy state.

[0078] Overall, a comparison of various indicators between areas remediated with screened humus and those remediated with traditional organic amendments shows that screened humus exhibits remediation effects comparable to those of organic amendments. Furthermore, since screened humus is a byproduct of integrated remediation of municipal solid waste landfills, the remediation cost is significantly reduced because there is no need to purchase this material.

[0079] Example 2

[0080] The remediation site in this embodiment is an abandoned site of an ion-adsorption rare earth mine in Guangdong Province. This abandoned site is characterized by poor soil physical structure, low acidity, poor nutrient content, high rare earth element content, and complete ecological degradation.

[0081] The experiment designed a remediation zone consisting of a mixture of sieved humus from a municipal solid waste landfill and waste soil, designated as Remediation Zone C. Simultaneously, a remediation zone consisting of a mixture of organic amendment (organic manure) and waste soil was established, designated as Remediation Zone D. The application rate of either sieved humus or organic amendment was 5 kg / m³. 2 This study investigates the effects of sieved humus from municipal solid waste landfills as a soil amendment on the physicochemical properties and biodiversity of soils in ion-adsorption rare earth mine waste sites, evaluates the remediation effect of this method, and compares it with the remediation effect of organic fertilizer.

[0082] A method for remediating acidic mines by screening humus from municipal solid waste landfills includes the following steps:

[0083] (1) Excavation of aged waste from a landfill in Guangdong Province. After long-term stable mineralization, the landfill can be preliminarily sorted by a screening machine to obtain humus soil with high nutrient content and rich microorganisms. The particle size of the humus soil after screening is less than 2 mm. Organic manure was purchased from a livestock farm in Guangdong.

[0084] (2) The sieved humus collected in step (1) is pretreated by air drying and crushing, including air drying to reduce the moisture content and mechanical screening to ensure uniform soil quality.

[0085] (3) The organic matter content, total nutrients (nitrogen, phosphorus, potassium) and heavy metal content of the sieved humus and organic manure pretreated in step (2) were analyzed in detail using laboratory analysis methods to assess whether they can be used as improved substrates.

[0086] (4) According to the component analysis results in step (3), as shown in Table 4, the component content of the screened humus and organic manure all meet the improvement substrate standard of "LY / T 1970—2011-Greening Organic Substrate".

[0087] (5) Then, the sieved humus and organic manure are separated at 10 kg / m³. 2 Apply the soil and till it to a depth of 10-15 cm to form a new soil layer. Investigate and analyze the organic matter, nutrient, and heavy metal content in the soil of the ion-adsorption rare earth mine wasteland after improvement with sieved humus and organic manure to assess its suitability for plant growth and potential risks. As shown in Table 5, the component content of both the sieved humus-improved soil and the organic manure-improved soil meets the standard of "CJ / T 340—2016-Green Planting Soil".

[0088] (6) Apply seeds of 10 kinds of mixed plants, such as native plants and pioneer plants, such as grass, legume, and chrysanthemum, to the soil layer after tilling in step (5).

[0089] (7) Finally, the vegetation growth status, soil quality, rare earth element content and other indicators of the improved restoration areas C and D in step (6) are monitored regularly to evaluate the restoration effect and restoration cost, so as to ensure that the expected ecological restoration goal is achieved.

[0090] Table 4. Results of pH, nutrient and heavy metal content in sieved humus and organic manure.

[0091]

[0092]

[0093] Table 5. Results of pH, nutrient, and heavy metal content in soil from ion-adsorption rare earth mine waste sites after sieving and improvement with humus and organic manure.

[0094]

[0095]

[0096] Note: ND means Not Detected.

[0097] Table 6. Results of soil physicochemical properties 12 months after remediation

[0098]

[0099] As shown in Table 6, compared with the remediation areas C and D, the soil pH value was effectively adjusted to a suitable acidity and alkalinity, creating a good environment for plant growth. The organic matter and nutrient content in the improved soil increased significantly, which not only provided abundant nutrition for plants but also enhanced the soil's water retention and aeration properties, which is conducive to plant growth and the healthy development of the soil ecosystem. At the same time, the available content of rare earth elements in the soil decreased significantly, effectively reducing the risks to plant growth and the natural environment.

[0100] like Figure 3 As shown in the figure, the comparison revealed that the coverage of repaired area C exceeded 95% after 12 months, while the coverage of repaired area D exceeded 85% after 12 months. Figure 4 As shown, after six months of natural succession, native species *Miscanthus sinensis* and *Pinus massoniana* emerged. In the early stages of the restoration process, the soil physical properties of restoration area C were superior to those of restoration area D, providing favorable conditions for rapid plant establishment and development. Restoration area C exhibited better recovery results in terms of plant cover and succession.

[0101] In summary, this invention, during mine remediation, effectively improves soil physicochemical properties and achieves heavy metal fixation by screening out the abundant organic matter and nutrients contained in humus. Furthermore, compared to traditional soil amendment materials, using screened humus enables the resource recovery of urban solid waste, reduces the consumption of natural resources, and lowers costs as a mine remediation material, meeting the requirements of sustainable development, compensating for non-renewable resources, and yielding significant environmental and social benefits.

[0102] Example 3

[0103] The remediation site in this embodiment is a tailings area of ​​a lead-zinc mine in Guangdong Province. This abandoned site is characterized by poor soil physical structure, low acidity, poor nutrient content, high heavy metal content, and complete ecological degradation.

[0104] The experiment designed a remediation area, designated as Remediation Area E, directly covered with a mixture of screened humus from a municipal solid waste landfill and garden soil in a 1:5 mass ratio. Simultaneously, a remediation area, designated as Remediation Area F, was covered with an organic amendment (organic manure) mixed with garden soil in a 1:5 mass ratio. The aim was to investigate the effects of screened humus from a municipal solid waste landfill as a soil amendment on the physicochemical properties and biodiversity of the soil in a lead-zinc mine tailings area, evaluate the remediation effect of this method, and compare it with the remediation effect of organic fertilizer.

[0105] A method for remediating acidic mines by screening humus from municipal solid waste landfills includes the following steps:

[0106] (1) Excavation of aged waste from a landfill in Guangdong Province. The landfill has undergone stable mineralization for more than ten years. After screening, nutrient-rich and microbial-rich humus soil can be initially obtained. The particle size of the humus soil after screening is less than 2 mm. Organic manure was purchased from a nearby farmer.

[0107] (2) The organic matter content, total nutrients (nitrogen, phosphorus, potassium) and heavy metal content in the sieved humus and organic manure in step (1) were analyzed in detail using laboratory analysis methods, as shown in Table 7. The results of the component analysis showed that the organic matter content, total nutrients (nitrogen, phosphorus, potassium) and heavy metal content in the organic manure met the standard of "LY / T 1970—2011-Organic substrate for greening". Except for the total nutrients, the sieved humus met the standard of "LY / T 1970—2011-Organic substrate for greening".

[0108] (3) The total nutrient content of the sieved humus collected in step (1) is adjusted by adding nitrogen-phosphorus-potassium compound fertilizer (15-15-15). The nitrogen-phosphorus-potassium compound fertilizer accounts for 2% of the mass of the sieved humus to meet the standard of "LY / T1970—2011-Organic substrate for greening". Then, it is air-dried and crushed for pretreatment, and mixed with garden soil at a ratio of 1:5 to obtain sieved humus improved soil. It is then mechanically sieved using a screening machine. The particle size of the sieved humus improved soil after screening is less than 2 mm to ensure uniform soil quality. The organic amendment purchased in step (1) is mixed with garden soil at a ratio of 1:5 to obtain organic improved soil. It is then mechanically sieved using a screening machine. The particle size of the humus after screening is less than 2 mm to ensure uniform soil quality.

[0109] (4) Laboratory analysis methods were used to conduct detailed analysis of the organic matter content, nutrients (such as nitrogen, phosphorus, and potassium), and heavy metal content in the pretreated sieved humus-improved soil and organic-improved soil from step (3) to assess their suitability for plant growth and potential risks. As shown in Table 8, the component content of the sieved humus-improved soil and organic-improved soil both met the standard of "CJ / T340—2016-Green Planting Soil".

[0110] (5) An investigation and analysis of the organic matter, nutrient, and heavy metal content in a lead-zinc mine tailings area in Guangdong Province was conducted. This area is characterized by strong acidity, severe heavy metal pollution, lack of soil cover, extreme nutrient deficiency, complete ecological degradation, and steep slopes. Considering factors such as maintaining slope stability, ease of construction, and long-term restoration, direct soil covering was used for remediation. The treated, screened humus-modified soil and organic-modified soil were then mixed at a concentration of 110-120 kg / m³. 2 The soil was directly applied to the experimental plots in the lead-zinc mine tailings area to be remediated, forming a new soil layer. The thickness of the covering was determined to be 10–15 cm based on the soil improvement requirements and vegetation growth characteristics.

[0111] (6) Apply seeds of 10 kinds of mixed plants, such as native plants and pioneer plants, such as grass, legume, and aster, to the soil after covering in step (5).

[0112] (7) Finally, the vegetation growth status of the improved restoration areas E and F in step (6) is monitored regularly, and 0-10cm mixed soil samples are collected using the five-point method to determine soil quality, heavy metal content and other indicators, and to evaluate the restoration effect and restoration cost, so as to ensure that the expected ecological restoration goal is achieved.

[0113] Table 7. Results of pH, nutrient and heavy metal content in sieved humus and organic manure.

[0114]

[0115] Table 8. Results of pH, nutrient and heavy metal content in sieved humus-modified soil and organic-modified soil.

[0116]

[0117] Table 9. Results of soil physicochemical properties test 6 months after remediation.

[0118]

[0119] As shown in Table 9, comparing remediation areas E and F, the soil pH was effectively regulated after remediation, the soil acid-base balance was improved, and suitable conditions were created for plant growth. The organic matter content and nutrient levels of the remediated soil were significantly improved, enhancing soil fertility. This not only provided necessary nutrition for plants but also helped improve soil water retention and aeration, thereby promoting plant growth and the health of the soil ecosystem. The available heavy metals were significantly reduced after remediation, reducing potential harm to plants and the environment.

[0120] like Figure 5 As shown, comparing restoration areas E and F, one month after restoration, the dominant species was the pioneer plant ryegrass. Restoration area E showed better growth rate and biomass than restoration area F. Simultaneously, germinating seeded plants such as clover and alfalfa were also observed. Twelve months after restoration, the coverage exceeded 95%, with 14 plant species, and the dominant species were the previously sown goosegrass and pigweed. Figure 6 As shown, after six months of natural succession, new species tolerant of poor soil conditions, such as Lantana and Solanum nigrum, have been added. During the restoration process, the initial planting of pioneer and native plants can quickly cover the soil surface, reduce erosion, and gradually restore ecosystem functions; in the later stages, species diversity and richness gradually increase, and the ecosystem develops towards greater stability and health.

[0121] Overall, in the remediation of extremely barren lead-zinc mine waste sites, a comparison of various indicators between areas remediated with screened humus and those remediated with traditional organic amendments shows that screened humus exhibits remediation effects comparable to organic amendments. Furthermore, since screened humus is a byproduct of integrated remediation of municipal solid waste landfills, the remediation cost is significantly reduced because there is no need to purchase this material.

[0122] Comparative Example 1

[0123] The difference between the remediation area A-CK1 and Example 1 is that the sifted humus in step (5) is used directly without mixing with garden soil. For example... Figure 7 As shown, due to excessively high organic matter content (25.37%), nutrient imbalance, and poor physical properties, the soil exhibited strong water absorption, excessive water retention, and poor aeration, resulting in poor root development of the vegetation. Six months after restoration, the coverage was only 50%, plant growth was slow, and localized waterlogging and root rot occurred.

[0124] Therefore, high organic matter needs to be diluted with low-nutrient soil in order to balance nutrients and physical structure.

[0125] Comparative Example 2

[0126] The repair area A-CK2 differs from Example 1 in that, in step (5), it is directly covered with garden soil (10cm) without adding sieved humus. For example... Figure 8 As shown, the improvement on soil properties was limited due to the low content of organic matter (1.15%) and available potassium (84.96 mg / kg) in the garden soil. With 75% vegetation cover, the available form of heavy metals decreased by 40%, making the effect significantly worse than that of sieved humus-based soil remediation.

[0127] Therefore, suitable soil physical structure and nutrient content are key factors in ensuring plant growth and restoration effectiveness.

[0128] Comparative Example 3

[0129] The repair area C-CK differs from Example 2 in that the tillage depth in step (5) is 5 cm. For example... Figure 9 As shown, due to the thinness of the improved layer and its distinct separation from the subsoil, root growth downwards was restricted, resulting in a vegetation coverage rate of only 60% in the remediated area (C-CK). The soil exhibited a large vertical pH gradient, with the surface layer at 6.8 and the lower layer at 4.5. Furthermore, the available rare earth elements in the lower layer decreased by only 30%, lower than the 97.38% reduction observed in Example 2. Therefore, tillage depth is a crucial step in ensuring uniform improvement.

[0130] Comparative Example 4

[0131] The difference between the remediation area E-CK1 and Example 3 is that no nitrogen, phosphorus, and potassium compound fertilizer was added in step (3) to adjust the total nutrients. Because the total nutrients in the sifted humus soil (2.11%) did not meet the standard of LY / T 1970—2011 (≥2.5%), the hydrolyzable nitrogen (98.34 mg / kg) and available phosphorus (18.22 mg / kg) in the improved soil were significantly lower than those in remediation area E. Figure 10 As shown, the plant is growing slowly and the leaves are turning yellow (symptoms of nitrogen deficiency).

[0132] Therefore, insufficient nutrients directly limit plant growth, verifying the necessity of adding inorganic fertilizers.

[0133] Comparative Example 5

[0134] The repair area E-CK2 differs from Example 3 in that the covering thickness in step (5) is 30 cm. Vegetation coverage reaches 95%, but the amount of material used is excessive (200-250 kg / m²). 2 The cost of the improved material is 200% higher than that of Example 3. It is economically inefficient, and excessive covering may cause slope instability (when the slope is >40°), such as... Figure 11 As shown.

[0135] Therefore, 10-15cm is the optimal thickness range, balancing effectiveness and cost.

[0136] Comparative Example 6

[0137] The difference between the remediation area E-CK3 and Example 3 is that the covering thickness in step (5) is 3 cm. If the modified layer is too thin, it cannot effectively isolate heavy metals, and plant roots die after contacting the contaminated subsoil. Figure 12 As shown, six months after remediation, the soil coverage was only 30%, and the soil pH dropped back to 4.2.

[0138] Therefore, a coverage thickness of ≥10cm is the critical value to ensure the repair effect.

[0139] The repair costs required in Examples 1-3 and Comparative Examples 1-6 were statistically analyzed and recorded, as shown in Table 10.

[0140] Table 10 Repair Costs

[0141]

[0142]

[0143]

[0144] Therefore, according to Table 10, the use of sieved humus soil requires nutrient adjustment (Comparative Examples 2 and 4), reasonable dilution (Comparative Example 1), and scientific construction (Comparative Examples 3, 5, and 6) to achieve the best results; a covering thickness of 10-15 cm is the optimal choice (Comparative Examples 5-6); the cost of the improved materials of this invention is only 26.9%-30% of that of the traditional method (using organic manure), and the ecological indicators are similar to or superior to those of the traditional method.

[0145] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for remediating acidic mines using humus soil screened from municipal solid waste landfills, characterized in that, Includes the following steps: (1) Excavate the domestic waste landfill to obtain old waste, crush and screen it to obtain screened humus; (2) Analyze the heavy metals in the screened humus. If it meets the Class III standard of "LY / T 1970—2011-Organic substrate for greening", then proceed to step (3). If it does not meet the Class III standard of "LY / T 1970—2011-Organic substrate for greening", then carry out harmless landfill treatment on the screened humus. (3) Analyze the organic matter and nutrients in the sieved humus. If the results of the component analysis meet the improvement substrate standard of "LY / T1970—2011-Greening Organic Substrate", then proceed to step (4) or (5); if the results do not meet the improvement substrate standard of "LY / T1970—2011-Greening Organic Substrate", then add an amendment. Determine the amount of amendment based on the soil analysis results and the characteristics of the amendment. Adjust the nutrient content of the sieved humus to meet the improvement substrate standard of "LY / T 1970—2011-Greening Organic Substrate", then proceed to step (4) or (5). (4) Analyze the site conditions of acid mine wasteland. For acid mine wasteland with gentle slope and soil cover, screened humus soil that meets the improvement substrate standard of "LY / T 1970—2011-Greening Organic Substrate" should be used as organic substrate. Improvement and plowing should be adopted for remediation. The amount of screened humus soil should be determined according to the nutrient analysis results of acid mine soil and the characteristics of screened humus soil. The organic matter and nutrient content in the mixed soil after plowing should meet the Class IV standard of "CJ / T 340—2016-Greening Planting Soil". (5) Analyze the site conditions of acid mine wasteland. For acid mine wasteland with steep slopes and no soil layer or thin soil cover, screened humus soil that meets the improvement substrate standard of "LY / T 1970—2011-Greening Organic Substrate" is used as organic substrate. It is mixed with low nutrient soil to dilute organic matter and directly covered to repair and form a new soil layer. The new soil layer should meet the Class IV standard of "CJ / T 340—2016-Greening Planting Soil". (6) Sow or plant vegetation on the improved soil; (7) Finally, the soil remediation effect is monitored and evaluated regularly.

2. The method for remediating acidic mines by screening humus from municipal solid waste landfills as described in claim 1, characterized in that, In step (2), the screened humus soil is pre-dried, crushed, and sieved.

3. The method for remediating acidic mines by screening humus from municipal solid waste landfills as described in claim 1, characterized in that, The heavy metals in step (2) include at least one of copper, iron, lead, zinc, cadmium, and chromium.

4. The method for remediating acidic mines by screening humus from municipal solid waste landfills as described in claim 1, characterized in that, The nutrients in step (3) include at least one of nitrogen, phosphorus, potassium, calcium, and magnesium.

5. The method for remediating acidic mines by screening humus from municipal solid waste landfills as described in claim 1, characterized in that, The improver in step (3) includes at least one of phosphate fertilizer, nitrogen fertilizer, potassium fertilizer, organic manure, biochar, crop residue, compost, and green manure.

6. The method for remediating acidic mines by screening humus from municipal solid waste landfills as described in claim 1, characterized in that, The acidic mine site conditions in step (4) or (5) include at least one of the following: topographic and geomorphological conditions, soil physicochemical properties, hydrological conditions, climatic conditions, biological conditions, and human interference factors.

7. The method for remediating acidic mines by screening humus from municipal solid waste landfills as described in claim 1, characterized in that, In step (4), for acidic mines with gentle slopes and soil cover, the screened humus soil that meets the improved substrate standard is mixed with the acidic mine waste soil at a mass ratio of (0.02-0.1):1, and then the mixed soil is covered on the surface of the acidic mine waste with a thickness of not less than 10cm.

8. The method for remediating acidic mines by screening humus from municipal solid waste landfills as described in claim 1, characterized in that, In step (5), for acid mines with steep slopes and no soil layer or thin soil layer, the screened humus soil that meets the improved substrate standard is mixed with low-nutrient soil at a mass ratio of 1:(3-10), and then the mixed soil is covered on the surface of the acid mine wasteland with a thickness of not less than 10cm.

9. The method for remediating acidic mines by screening humus from municipal solid waste landfills as described in claim 1, characterized in that, The low-nutrient soil in step (5) includes at least one of garden soil, sandy soil, clay, and construction waste soil.

10. The method for remediating acidic mines by screening humus from municipal solid waste landfills as described in claim 1, characterized in that, In step (6), native and pioneer plant species adapted to the acidic mine wasteland environment are selected for sowing or planting; And / or, the monitoring indicators in step (7) include soil quality parameters, vegetation coverage, plant growth status and heavy metal content in the soil.

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