Method for passivating heavy metals in soil by using fulvic acid type functional bacterial fertilizer and application

Abstract

The invention discloses a method for passivating heavy metals in soil by fulvic acid type functional bacterial fertilizer and application, and relates to the technical field of organic agriculture. According to the method, by preparing the fulvic acid type functional bacterial fertilizer, cationic heavy metals in soil are effectively passivated, absorption of crops to the heavy metals is reduced, and the safety of agricultural products is ensured. The preparation method comprises the following steps: crushing dry wood chips, mixing the crushed wood chips with manure with the water content of 70-80%, and adding a decomposition agent for decomposition to prepare a fulvic acid type organic fertilizer A; attapulgite and diatomite are used as carriers, ammonium dihydrogen phosphate and bacillus subtilis are mixed, and a functional bacterial fertilizer B is prepared; mixing A, B and starch glue in proportion to prepare particles C; during application, the particles C are applied to polluted soil according to 0-300 kg / mu, rice is planted, and experiments show that the Cd content of rice seeds is remarkably reduced to 0.05-0.24 mg / kg, and the rice seeds meet the food safety standard. According to the method, heavy metal is efficiently passivated through the synergistic effect of fulvic acid, BS and nano clay, meanwhile, nutrients are provided, and crop growth is promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of organic agriculture, and specifically to a method and application for passivating heavy metals in soil by a fulvic acid-type functional bacterial fertilizer. Background Art

[0002] Soil heavy metal pollution is one of the major environmental problems that urgently need to be solved globally. With the rapid development of industrialization, urbanization, and agricultural intensification, heavy metals such as cadmium (Cd(II)) and lead (Pb(II)) enter the soil through industrial wastewater, atmospheric deposition, the use of chemical fertilizers and pesticides, etc., and gradually accumulate in the soil. These heavy metal pollutants not only damage the ecological functions of the soil, affect soil fertility and the normal growth of crops, but also enter the human body through the food chain, posing a serious threat to human health. For example, cadmium may cause diseases such as kidney damage and osteoporosis, while lead is significantly toxic to the nervous system, especially the intellectual development of children. Therefore, the treatment and remediation of soil heavy metal pollution have become important topics in environmental science and agricultural science research. Developing efficient, economical, and environmentally friendly heavy metal-contaminated soil remediation technologies not only has important significance for ensuring food security and the stability of the ecosystem, but also has a profound impact on promoting the sustainable development of green agriculture.

[0003] At present, the remediation technologies for soil heavy metal pollution are mainly divided into three categories: physical remediation, chemical remediation, and biological remediation. These methods have achieved certain results both theoretically and practically, but they also have their own limitations and are difficult to fully meet the actual application requirements. Physical remediation methods mainly remove or isolate heavy metal pollutants in the soil through physical means. Common physical remediation technologies include soil replacement method, pyrolysis method, and soil tillage dilution method, etc. The soil replacement method reduces the heavy metal concentration by replacing the polluted soil or covering it with clean soil. The pyrolysis method uses high temperature to volatilize heavy metals or convert them into forms that are not easily migratory. These methods can reduce the content of heavy metals in the soil to a certain extent in a short time, but their application is significantly limited. First of all, the cost of physical remediation is extremely high. Especially for the soil replacement method, a large amount of clean soil resources are required, which is almost infeasible in the remediation of large-area polluted soil. Secondly, these methods often cause irreversible damage to the soil structure and fertility. For example, the pyrolysis method may lead to the loss of organic matter and microbial communities in the soil, making the soil lose its agricultural production capacity. In addition, physical remediation is usually only applicable to small-scale, high-concentration polluted areas and is difficult to be extended to the treatment of wide-area farmland soil. Chemical remediation methods change the forms of heavy metals or remove them from the soil by adding chemical reagents, thereby reducing their bioavailability and toxicity. Common chemical remediation technologies include solidification / stabilization, soil washing, and chemical precipitation, etc. Solidification / stabilization converts heavy metals into insoluble compounds by adding substances such as lime and phosphate. Soil washing extracts heavy metals from the soil using acidic solutions or chelating agents. These methods can significantly reduce the mobility and plant absorption rate of heavy metals in the short term and have a certain degree of rapidity and efficiency. However, chemical remediation also has obvious deficiencies. First of all, the use of chemical reagents may introduce new pollutants. For example, the acidic solution used in the washing process may cause soil acidification and damage the physical and chemical properties of the soil. Secondly, the effect of solidification / stabilization may be weakened due to environmental conditions (such as rainfall, pH change), and there is still a risk of heavy metals being re-released. In addition, the cost of chemical remediation is relatively high, and it has a greater impact on the soil ecosystem, which is not conducive to the long-term restoration of soil functions. Biological remediation uses the metabolic activities of plants, microorganisms, or other organisms to absorb, transform, or immobilize heavy metals in the soil, with the characteristics of environmental protection and sustainability. Phytoremediation absorbs heavy metals by planting hyperaccumulator plants (such as Pteris vittata, Sedum alfredii Hance). Microbial remediation uses the metabolic functions of certain strains (such as sulfate-reducing bacteria) to immobilize or transform heavy metals into low-toxic forms. The advantage of biological remediation is that it is environmentally friendly, avoids secondary pollution of chemical reagents, and can improve the soil ecosystem while remediating heavy metals. However, the disadvantages of biological remediation are also prominent. First of all, the remediation cycle is relatively long, usually taking several months or even years to achieve significant results, and it is not applicable to polluted scenarios that need to be treated urgently. Secondly, the remediation effect is greatly limited by environmental conditions. Factors such as soil pH, temperature, humidity, and heavy metal concentration will affect the activities of plants or microorganisms.In addition, after phytoremediation, the plants enriched with heavy metals need to be properly treated, otherwise the risk of secondary pollution may be caused.

[0004] In view of the limitations of traditional remediation technologies, in recent years, researchers have begun to explore composite remediation methods that combine multiple technologies to achieve higher efficiency and better environmental benefits. Among them, the remediation strategy of combining organic fertilizer with microbial technology has gradually attracted attention. Organic fertilizer can provide nutrients for the soil and improve the soil structure, while microorganisms change the forms of heavy metals or enhance the self-remediation ability of the soil through their metabolic activities. For example, fulvic acid, as a natural organic matter, has strong complexing ability and can form stable complexes with heavy metal ions, thereby reducing their bioavailability and toxicity. At the same time, beneficial microorganisms such as Bacillus subtilis (BS) can secrete various enzymes and metabolites, promote the decomposition of soil organic matter and nutrient release, and enhance the biological activity of the soil. In addition, nanomaterials such as nanoclays (attapulgite, diatomite, etc.) have also been introduced into the field of soil remediation due to their high specific surface area and strong adsorption ability to fix heavy metal ions and reduce their migration and bioavailability.

[0005] However, most of the organic fertilizers and microbial inoculants on the market are single-function products at present. For example, they only provide nutrients or only have a certain heavy metal passivation ability, and it is difficult to meet the multiple requirements of soil heavy metal remediation, nutrient supply and soil improvement at the same time. Therefore, developing a multifunctional remediation material that integrates heavy metal passivation, nutrient supply and soil improvement has become a research hotspot and urgent need in the field of soil pollution control.

[0006] In view of the deficiencies of traditional technologies and the limitations of existing products, the present invention proposes a preparation method of fulvic acid-based functional bacterial fertilizer and its application in the remediation of soil heavy metal pollution. This method prepares functional bacterial fertilizer particles by compounding fulvic acid-based organic fertilizer with materials such as Bacillus subtilis (BS), ammonium dihydrogen phosphate and nanoclay. This kind of functional bacterial fertilizer can not only effectively passivate cationic heavy metals (such as Cd(II) and Pb(II)) in the soil, reduce their bioavailability and plant absorption rate, but also provide essential nutrients for crops, promote crop growth, and at the same time improve the physical and chemical properties of the soil, with significant comprehensive advantages. The background technology of the present invention is based on a profound understanding of the current situation of soil heavy metal pollution and a comprehensive analysis of the limitations of traditional remediation technologies, aiming to provide an efficient, environmentally friendly and economical new solution for soil heavy metal pollution control through the synergistic effect of organic fertilizer, microorganisms and nanomaterials. The development of this fulvic acid-based functional bacterial fertilizer not only fills the gap in multifunctionality of the existing technology, but also provides new technical support for achieving the goals of green agriculture and sustainable development. Summary of the Invention

[0007] The existing technologies have various deficiencies in soil heavy metal remediation, and the specific problems are as follows: Traditional soil heavy metal remediation technologies, including physical remediation, chemical remediation, and biological remediation methods, show significant differences in performance under different soil conditions and heavy metal types, making it difficult to ensure stable and efficient remediation effects. For example, in chemical remediation, commonly used solidifying agents are prone to losing their effectiveness in acidic soil environments; while the effect of biological remediation highly depends on the activity of soil microorganisms and external environmental conditions, which limits its applicability. Chemical remediation methods usually require the use of a large amount of chemical reagents, and these reagents may introduce new pollution problems. For example, acidic solutions may cause soil acidification, and the residues of chelating agents may pose potential hazards to the environment. On the other hand, physical remediation technologies (such as soil replacement method and pyrolysis method) may damage the original structure and ecological functions of the soil, thereby affecting the long-term sustainable use of the soil. Although biological remediation technologies have certain environmental protection advantages, their remediation cycle is relatively long, usually taking several months or even years, and cannot meet the actual needs of emergency pollution treatment. Taking phytoremediation as an example, its process is slow, and improper treatment of the plants after remediation may lead to the re-release of heavy metals into the environment. The implementation costs of physical and chemical remediation technologies are usually relatively high, especially in the remediation of large areas of polluted soil, and the economy is poor. For example, the soil replacement method requires a large amount of clean soil resources as a substitute, the pyrolysis method consumes a huge amount of energy, and the investment in reagents and equipment required for chemical remediation is also very expensive. Most of the current organic fertilizer and microbial inoculant products on the market have single functions. For example, they can only provide nutrients or only have a certain heavy metal passivation ability, and it is difficult to simultaneously meet the comprehensive needs of soil heavy metal remediation, nutrient supply, and soil improvement. The existing technologies generally lack a comprehensive solution that effectively combines heavy metal passivation, nutrient supply, and soil improvement. This limitation makes it difficult for the existing methods to take into account the promotion of soil health and crop growth while remediating soil heavy metal pollution.

[0008] In view of the above problems, the present invention proposes a preparation method and application of a fulvic acid-type functional bacterial fertilizer, aiming to provide an efficient, stable, and environmentally friendly solution to achieve the remediation of soil heavy metal pollution, while providing nutrients for crops and improving soil quality.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A method for passivating heavy metals in soil with fulvic acid-type functional bacterial fertilizer, by weight, comprises the following steps: (1) Prepare fulvic acid-type organic fertilizer A: Crush 350-450 parts of dry wood chips to 30-50 mesh, take 120-150 parts of the crushed wood chips and add them to 400-500 parts of feces with a water content of 70-80%, adjust the water content to 45-55%, add 36-45 parts of a composting agent, and compost for 1-2 h. When the temperature reaches 80-90 °C, obtain fulvic acid-type organic fertilizer A with the water content reduced to 35-40% and the fulvic acid content of 7-9%; (2) Prepare functional bacterial fertilizer B: Mix 38-42 parts of attapulgite clay with 100-200 mesh and 38-42 parts of diatomite with 100-200 mesh as carriers, and mix them evenly with 8-12 parts of ammonium dihydrogen phosphate and 8-12 parts of Bacillus subtilis to obtain functional bacterial fertilizer B; (3) Prepare organic functional bacterial fertilizer granules C: Use the rolling granulation method to make organic functional bacterial fertilizer granules C with a particle size of 2-5 mm from organic fertilizer A, functional bacterial fertilizer B and starch glue in a mass ratio of (78-82):(8-12):(8-12); (4) Application treatment: Apply the organic functional bacterial fertilizer granules C to the soil polluted by heavy metals and plant rice. When the rice is mature, detect the contents of Cd and Pb in the seeds.

[0011] Preferably, the preparation method of the starch glue in step (3) is as follows: Mix corn starch, calcium oxide and deionized water in a mass ratio of 10:5:85 and carry out oxidation treatment for 40 min.

[0012] Preferably, in step (1), the dry wood chips are crushed to 40 mesh.

[0013] Preferably, in step (1), the water content of the feces is 75%.

[0014] Preferably, in step (1), the composting agent is molasses and dry yeast, and the mass ratio of the two is 1:(3-5).

[0015] Preferably, in step (2), the Latin name of Bacillus subtilis is Bacillussubtilis, and its number is ATCC6051.

[0016] Preferably, the parameters of the rolling granulation method in step (3) are as follows: The pressure of the pressing roller during pre-pressing is 0.8 MPa, and the pressure of the pressing roller during fine pressing is 1.5 MPa.

[0017] Preferably, the application parameters of the organic functional bacterial fertilizer granules C in step (4) are as follows: The row spacing of the broadcaster is 40 cm, and the traveling speed is 3-5 km / h.

[0018] The method as described above is applied to passivate heavy metals in soil.

[0019] Beneficial effects

[0020] (1)Highly efficient passivation of heavy metals: Through the synergistic effect of fulvic acid, Bacillus subtilis (BS), and nano-clay, the present invention can highly efficiently passivate cationic heavy metals in the soil, such as Cd(II) and Pb(II). The experimental results show that after applying the method of the present invention, the Cd content in rice seeds is significantly reduced to 0.05 - 0.24 mg / kg, far lower than the Cd content of 0.41 mg / kg in the untreated soil, meeting the requirements of GB2762-2022 "National Food Safety Standard Limits of Contaminants in Foods". This effect effectively reduces the bioavailability and plant absorption rate of heavy metals, ensuring the safety of agricultural products.

[0021] (2)Providing nutrients to promote growth: The functional bacterial fertilizer contains nutrients such as ammonium dihydrogen phosphate, which can provide essential nutrient elements for crops and promote the healthy growth of crops. At the same time, the addition of fulvic acid-based organic fertilizer further enhances the soil fertility, providing rich organic matter and trace elements for crops, which helps to improve the crop yield and quality.

[0022] (3)Improving soil quality: The synergistic effect of organic fertilizer and microorganisms can improve the physical and chemical properties of the soil, increase the organic matter content of the soil, improve the water-holding and fertilizer-holding capacity of the soil, and enhance the ecological function of the soil. This not only helps to restore the natural fertility of the soil but also promotes the healthy development of the soil ecosystem, laying a foundation for long-term agricultural production.

[0023] (4)Environmental protection and sustainability: The present invention uses natural organic substances and microorganisms as the main components, reducing the dependence on chemical reagents and avoiding the risk of secondary pollution. Fulvic acid, Bacillus subtilis, etc. are all environmentally friendly materials, meeting the concepts of green agriculture and sustainable development, and providing support for ecological environmental protection.

[0024] (5)Economy and easy promotion: Compared with traditional physical and chemical remediation methods, the method of the present invention has a lower cost, a simple preparation process, and is easy to produce and apply on a large scale. The application method of the functional bacterial fertilizer is flexible and can be adjusted according to the soil pollution degree and crop requirements, having a wide application prospect and being particularly suitable for promotion and use in heavy metal polluted areas.

[0025] In summary, through the preparation and application of fulvic acid-based functional bacterial fertilizer, the present invention realizes multiple goals of highly efficient remediation of soil heavy metal pollution, nutrient supply, and soil quality improvement, providing effective technical support for ensuring the safety of agricultural products and promoting the sustainable development of agriculture. Description of the Drawings

[0026] Figure 1It is the detection report of heavy metals in rice presented in Example 2. (A: First page of the report; B: Without adding organic functional bacterial fertilizer; C: Adding 150 Kg / mu of organic functional bacterial fertilizer; D: Adding 300 Kg / mu of organic functional bacterial fertilizer).

[0027] Figure 2 It is the changing trends of soluble Cd(II) and Pb(II) with pH and time in Example 2. (Cd(II): (A), (B); Pb(II): (C), (D)). Detailed implementation methods

[0028] For the embodiments of the present invention, parts by weight or parts by mass are equivalently replaced with kilograms (Kg) or grams (g), and can be scaled up or down in the same proportion, with little impact on the experimental results.

[0029] Example 1: Preparation and application under standard conditions

[0030] Prepare humic acid type organic fertilizer A. Raw materials: Dry wood chips: 400 parts, crushed to 40 mesh. Feces: 450 parts, with a moisture content of 75%. Process: Take 135 parts of crushed wood chips and add them to the feces, mix evenly, and adjust the moisture content to 50%. Add 40 parts of a composting agent (prepared from molasses and dry yeast in a mass ratio of 1:4), stir and then carry out composting. The composting time is 1.5 h, and control the temperature to reach 85 °C. Result: The moisture content of organic fertilizer A is 37%, and the humic acid content is 8%. Prepare functional bacterial fertilizer B. Raw materials: Attapulgite: 40 parts, crushed to 150 mesh. Diatomite: 40 parts, crushed to 150 mesh. Ammonium dihydrogen phosphate: 10 parts. Bacillus subtilis (ATCC6051): 10 parts. Process: Mix the above raw materials evenly to make functional bacterial fertilizer B. Prepare organic functional bacterial fertilizer granules C. Raw material ratio: Organic fertilizer A: Functional bacterial fertilizer B: Starch glue = 80:10:10. Starch glue preparation: Mix corn starch, calcium oxide, and deionized water in a mass ratio of 10:5:85, and carry out oxidation treatment for 40 min. Process: After mixing organic fertilizer A, functional bacterial fertilizer B, and starch glue, use a rolling granulation process with a pre-pressing pressure of 0.8 MPa and a fine-pressing pressure of 1.5 MPa to make granules with a particle size of 3 mm. Apply the treatment. Method: Application rate: 150 kg / mu, use a broadcaster, row spacing 40 cm, traveling speed 4 km / h. Result: Cd content in rice seeds: 0.15 mg / kg, Pb content: 0.08 mg / kg. Analysis: Compared with untreated soil (Cd content 0.41 mg / kg), the Cd content is significantly reduced, meeting the food safety standard, indicating a good repair effect under standard conditions.

[0031] Example 2: Low wood chip usage and high composting temperature

[0032] Preparation of fulvic acid type organic fertilizer A. Raw materials: dried wood chips: 350 parts, crushed to 30 mesh. Feces: 400 parts, with a moisture content of 70%. Process: Take 120 parts of crushed wood chips and add them to the feces, mix evenly, and adjust the moisture content to 45%. Add 36 parts of a composting agent (prepared from molasses and dry yeast in a mass ratio of 1:3), compost for 1 h, and control the temperature at 90 °C. Result: The moisture content of organic fertilizer A is 40%, and the fulvic acid content is 7%. Preparation of functional bacterial fertilizer B. Raw materials: attapulgite: 38 parts, crushed to 100 mesh. Diatomite: 38 parts, crushed to 100 mesh. Ammonium dihydrogen phosphate: 8 parts. Bacillus subtilis: 8 parts. Process: Mix the raw materials evenly to make functional bacterial fertilizer B. Preparation of organic functional bacterial fertilizer granules C. Raw material ratio: organic fertilizer A: functional bacterial fertilizer B: starch glue = 78:8:8. The starch glue is prepared in the same way as in Example 1. Process: Roll granulation to make granules with a particle size of 2 mm. Application treatment. Method: Application rate: 50 kg / mu. Result: Cd content in rice seeds: 0.24 mg / kg, Pb content: 0.12 mg / kg. Analysis: The Cd content is lower than that of the untreated soil but higher than that of Example 1, indicating that lower application rates and wood chip amounts have certain limitations on the remediation effect.

[0033] Example 3: High wood chip amount and low composting temperature

[0034] Preparation of fulvic acid type organic fertilizer A. Raw materials: dried wood chips: 450 parts, crushed to 50 mesh. Feces: 500 parts, with a moisture content of 80%. Process: Take 150 parts of crushed wood chips and add them to the feces, adjust the moisture content to 55%. Add 45 parts of a composting agent (prepared from molasses and dry yeast in a mass ratio of 1:5), compost for 2 h, and control the temperature at 80 °C. Result: The moisture content of organic fertilizer A is 35%, and the fulvic acid content is 9%. Preparation of functional bacterial fertilizer B. Raw materials: attapulgite: 42 parts, crushed to 200 mesh. Diatomite: 42 parts, crushed to 200 mesh. Ammonium dihydrogen phosphate: 12 parts. Bacillus subtilis: 12 parts. Process: Mix evenly to make functional bacterial fertilizer B. Preparation of organic functional bacterial fertilizer granules C. Raw material ratio: organic fertilizer A: functional bacterial fertilizer B: starch glue = 82:12:12. The starch glue is prepared in the same way as in Example 1. Process: Roll granulation to make granules with a particle size of 5 mm. Application treatment. Method: Application rate: 300 kg / mu. Result: Cd content in rice seeds: 0.05 mg / kg, Pb content: 0.03 mg / kg. Analysis: The Cd and Pb contents are extremely low, indicating that high application rates and high wood chip amounts significantly improve the remediation effect.

[0035] Example 4: Remediation of moderately polluted soil

[0036] Preparation of fulvic acid type organic fertilizer A, raw materials: dried wood chips: 400 parts, crushed to 40 mesh. Feces: 450 parts, water content 75%. Process: Take 135 parts of crushed wood chips and add them to the feces, adjust the water content to 50%. Add 40 parts of a composting agent (prepared from molasses and dry yeast in a mass ratio of 1:4), compost for 1.5 h, and the temperature reaches 85 °C. Result: The water content of organic fertilizer A is 37%, and the fulvic acid content is 8%. Preparation of functional bacterial fertilizer B, raw materials: attapulgite: 40 parts, crushed to 150 mesh. Diatomite: 40 parts, crushed to 150 mesh. Ammonium dihydrogen phosphate: 10 parts. Bacillus subtilis: 10 parts. Process: Mix evenly to make functional bacterial fertilizer B. Preparation of organic functional bacterial fertilizer granules C, raw material ratio: organic fertilizer A: functional bacterial fertilizer B: starch glue = 80:10:10. The starch glue is prepared in the same way as in Example 1. Process: Roll granulation to make granules with a particle size of 3 mm. Application treatment, method: application rate: 200 kg / mu, the soil is at a medium pollution level. Result: Cd content in rice seeds: 0.10 mg / kg, Pb content: 0.05 mg / kg. Analysis: In medium-polluted soil, the Cd content is far lower than the standard limit value, and the remediation effect is good.

[0037] Example 5: Remediation of severely polluted soil

[0038] Preparation of fulvic acid type organic fertilizer A, raw materials: dried wood chips: 450 parts, crushed to 50 mesh. Feces: 500 parts, water content 80%. Process: Take 150 parts of crushed wood chips and add them to the feces, adjust the water content to 55%. Add 45 parts of a composting agent (prepared from molasses and dry yeast in a mass ratio of 1:5), compost for 2 h, and the temperature reaches 90 °C. Result: The water content of organic fertilizer A is 35%, and the fulvic acid content is 9%. Preparation of functional bacterial fertilizer B, raw materials: attapulgite: 42 parts, crushed to 200 mesh. Diatomite: 42 parts, crushed to 200 mesh. Ammonium dihydrogen phosphate: 12 parts. Bacillus subtilis: 12 parts. Process: Mix evenly to make functional bacterial fertilizer B. Preparation of organic functional bacterial fertilizer granules C, raw material ratio: organic fertilizer A: functional bacterial fertilizer B: starch glue = 82:12:12. The starch glue is prepared in the same way as in Example 1. Process: Roll granulation to make granules with a particle size of 5 mm. Application treatment, method: application rate: 300 kg / mu, the soil is at a severely polluted level. Result: Cd content in rice seeds: 0.08 mg / kg, Pb content: 0.04 mg / kg. Analysis: In severely polluted soil, the Cd and Pb contents are significantly reduced, and the remediation effect is still remarkable.

[0039] The above 5 examples demonstrate the preparation methods of fulvic acid type functional bacterial fertilizers under different preparation conditions (such as wood chip dosage, composting temperature, etc.) and application rates, as well as their remediation effects on the Cd and Pb contents of rice seeds. By adjusting the parameters and application rates, this method shows good applicability and high efficiency in slightly, moderately, and severely polluted soils, providing specific guidance for practical applications.

[0040] Meanwhile, Example 6 was set up with the following scheme: Take 400 g of dry cassava residue, crush it to 40 mesh with a crusher. Take 135 g of the crushed cassava residue and add it to 450 g of pig manure with a moisture content of 75%. Adjust the moisture content to 50%, and then add 40 g of self-developed nano composting agent. The entire composting process takes 1.5 h, and the highest temperature reaches 85 °C (for 10 min) to obtain humic acid-type organic fertilizer A with a moisture content that can be reduced to 37% and a humic acid content of 8%. Mix 40 g of attapulgite (150 mesh) and 40 g of diatomite (150 mesh) as carriers with 10 g of potassium dihydrogen phosphate and 10 g of Bacillus subtilis evenly to obtain functional bacterial fertilizer B. Extrusion granulation is carried out on organic fertilizer A, functional bacterial fertilizer B, and starch glue (10 wt% corn starch + 5 wt% CaO2 + 85 wt% deionized water oxidized for 40 minutes) in a mass ratio of 82:8:12 to obtain organic functional bacterial fertilizer granules C (particle size 5 mm). Apply the organic functional bacterial fertilizer granules C to the soil contaminated with Cd(II) and Pb(II) at a rate of 150 kg / mu and plant rice. When the rice is mature, detect the Cd and Pb contents in the seeds. As Figure 1 shown, the results show that the Cd content in the rice with the addition of functional bacterial fertilizer can reach 0.15 mg / kg, while the Cd content in the rice without the addition of functional bacterial fertilizer reaches 0.41 mg / kg, which does not meet the standard requirements of GB2762-2022 "National Food Safety Standard Limits of Contaminants in Foods". In the above process, the changing trends of soluble Cd(II) and Pb(II) with pH and time are as Figure 2 shown. Specific operation steps: The influence of pH change on the removal rates of Cd(II) and Pb(II), the specific operation steps are as follows: Place 0.04 g of organic functional bacterial fertilizer in 30 mL of Cd(II) (20 mg / L) solution with different pH values, and then place it obliquely in a shaking incubator at a constant temperature of 28 °C and a rotation speed of 250 r / min; After 24 h, centrifuge for 5 min with the rotation speed adjusted to 7000 r / min. The supernatant passes through a 0.45 μm water-based filter membrane, measure the Cd(II) content in the filtrate, and calculate the Cd(II) removal efficiency. The measurement method of Pb(II) is the same as the above method. The influence of time change on the removal rates of heavy metal ions, the specific operation steps are as follows: Place 0.04 g of organic functional bacterial fertilizer in 30 mL of Cd(II) (20 mg / L) solution, and then place it obliquely in a shaking incubator at a constant temperature of 28 °C and a rotation speed of 250 r / min; After 5 min, 10 min, 20 min, 30 min, 1 h, 2 h, 4 h, 6 h, 8 h, 10 h, 14 h, 18 h, 24 h, centrifuge for 5 min with the rotation speed adjusted to 7000 r / min. The supernatant passes through a 0.45 μm water-based filter membrane, measure the Cd(II) content in the filtrate, and calculate the Cd(II) removal efficiency. The measurement method of Pb(II) is the same as the above method.

[0041] The above describes in detail the preferred embodiments of the present patent. However, the present patent is not limited to the above embodiments, and various changes can be made without departing from the gist of the present patent within the scope of knowledge possessed by those of ordinary skill in the art.

Claims

1. A method for passivating heavy metals in soil using fulvic acid-type functional bacterial fertilizer, characterized in that: The method comprises the following steps, in parts by weight: (1) preparing humic acid type organic fertilizer A: crush 350-450 parts of dry sawdust into 30-50 mesh, take 120-150 parts of the crushed sawdust and add it to 400-500 parts of feces with a moisture content of 70-80%, adjust the moisture content to 45-55%, add 36-45 parts of a composting agent, and compost for 1-2 hours. When the temperature reaches 80-90°C, humic acid type organic fertilizer A is obtained, the moisture content is reduced to 35-40%, and the humic acid content is 7-9%; (2) preparing functional bacterial fertilizer B: crush 38-42 parts of 100-200 mesh concave-convex Stick soil and 38-42 parts of 100-200 mesh diatomaceous earth are used as carriers, mixed with 8-12 parts of diammonium phosphate and 8-12 parts of Bacillus subtilis to obtain functional bacterial fertilizer B; (3) Preparation of organic functional bacterial fertilizer granules C: Organic fertilizer A, functional bacterial fertilizer B and starch glue are mixed in a mass ratio of (78-82): (8-12): (8-12) by rolling granulation method to prepare organic functional bacterial fertilizer granules C with a particle size of 2-5 mm; (4) Application treatment: The organic functional bacterial fertilizer granules C are applied to soil contaminated by heavy metals and rice is planted. When the rice is mature, the Cd and Pb contents in the seeds are detected.

2. The method for passivating heavy metals in soil by using fulvic acid type functional bacterial fertilizer according to claim 1, characterized in that: The preparation method of starch glue in step (3) is as follows: corn starch, calcium oxide and deionized water are mixed in a mass ratio of 10:5:85 and oxidized for 40 minutes.

3. The method for passivating heavy metals in soil by using fulvic acid type functional bacterial fertilizer according to claim 1, characterized in that: In step (1), the dried wood chips are crushed to 40 mesh.

4. The method for passivating heavy metals in soil by using fulvic acid type functional bacterial fertilizer according to claim 1, characterized in that: In step (1), the moisture content of the feces is 75%.

5. The method for passivating heavy metals in soil using fulvic acid type functional bacterial fertilizer according to claim 1, characterized in that: In step (1), the composting agents are molasses and dry yeast, and the mass ratio of the two is 1:(3-5).

6. The method for passivating heavy metals in soil using fulvic acid type functional bacterial fertilizer according to claim 1, characterized in that: The Latin name of Bacillus subtilis in step (2) is Bacillus subtilis, and its number is ATCC6051.

7. The method for passivating heavy metals in soil using fulvic acid type functional bacterial fertilizer according to claim 1, characterized in that: The parameters of the roller granulation method in step (3) are as follows: the roller pressure during pre-pressing is 0.8 MPa, and the roller pressure during fine pressing is 1.5 MPa.

8. The method for passivating heavy metals in soil using fulvic acid type functional bacterial fertilizer according to claim 1, characterized in that: In step (4), the application parameters of the organic functional fertilizer particles C are as follows: the row spacing of the spreader is 40 cm, and the travel speed is 3-5 km / h.

9. Use of the method according to any one of claims 1 to 8 in passivating heavy metals in soil.

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