Method for repairing polluted cultivated land soil based on microorganisms

Abstract

The invention belongs to the technical field of soil improvement, and relates to a method for repairing polluted cultivated land soil based on microorganisms, which comprises the following steps: respectively domesticating bacillus subtilis, rhodopseudomonas and saccharomyces cerevisiae aiming at organic pollutants and heavy metal pollutants to improve the degradation and endurance capacities of the bacillus subtilis, the rhodopseudomonas and the saccharomyces cerevisiae; and preparing the thalli into the microbial capsule with high stability and activity. According to the pollution degree, the microbial capsules, the organic-inorganic repairing agent and the composite nutrient in different proportions are precisely applied in different areas, and plastic film mulching, regular shallow ploughing and bio-organic fertilizer application are combined to form a set of complete repairing system. According to the invention, synergistic degradation of multiple pollutants, long-acting effect of microorganisms and synchronous restoration of soil ecological functions are realized. The method has the outstanding advantages of being high in remediation efficiency, environmentally friendly, controllable in cost, wide in applicability and the like, and a reliable technical approach is provided for safe utilization and sustainable treatment of polluted cultivated land.

Description

Technical Field

[0001] This invention belongs to the technical field of soil improvement and relates to a method for remediating contaminated farmland soil based on microorganisms. Background Technology

[0002] With the intensification of industrialization and agricultural activities, soil pollution in arable land has become increasingly serious. The main pollutants include heavy metals (such as cadmium and lead) and organic pollutants (such as polycyclic aromatic hydrocarbons and pesticides). These pollutants not only affect crop growth and agricultural product safety but may also endanger human health through the food chain. Therefore, the remediation of contaminated soil has become an important issue in the environmental field. Existing remediation methods mainly include physical, chemical, and biological remediation technologies.

[0003] Physical remediation methods, such as topsoil replacement, soil exchange, and deep tillage, reduce soil pollution by displacing or diluting contaminants. However, these methods are labor-intensive, costly, and may damage soil structure and ecological functions, leading to secondary pollution. Chemical remediation methods, such as chemical immobilization, leaching, and redox reactions, stabilize or degrade contaminants by adding chemical reagents. However, these methods may introduce exogenous chemicals, alter soil pH and microbial communities, and even produce toxic byproducts, potentially having negative long-term effects on soil health.

[0004] Bioremediation methods have gained attention due to their environmental friendliness and sustainability, primarily including phytoremediation and microbial remediation. Phytoremediation utilizes hyperaccumulating plants to absorb and enrich pollutants, but it suffers from long remediation cycles, low efficiency, and limitations imposed by plant growth conditions and pollutant types. Microbial remediation utilizes microorganisms to degrade or transform pollutants, but current technologies often rely on single microbial species, offering limited effectiveness for soils with complex contamination. Furthermore, microorganisms in the field are susceptible to factors such as temperature, pH, and nutrient competition, resulting in low survival rates and activity, leading to unstable remediation outcomes. Many microbial remediation technologies lack zoned management of contaminated soil, hindering precise remediation and causing resource waste. Summary of the Invention

[0005] To address the above problems, this invention provides a method for remediating contaminated farmland soil based on microorganisms, specifically including the following steps: Step 1: Bacillus subtilis, Rhodopseudomonas erythrosporum, and Saccharomyces cerevisiae were inoculated separately into liquid culture media containing different contaminants and cultured at 28-32℃ and 100-200 rpm for 45-51 h with shaking. The liquid culture medium inoculated with Bacillus subtilis contained 0.8-1.2 mg / L benzo[a]pyrene, the liquid culture medium inoculated with Rhodopseudomonas erythrosporum contained 1.8-2.2 mg / L methyl parathion, and the liquid culture medium inoculated with Saccharomyces cerevisiae contained 1.8-2.2 mg / L Cd. 2+and 4.5-5.5 mg / L Pb 2+ .

[0006] Step two: After culturing, take 4-6% of the culture medium and transfer it to a liquid culture medium containing a higher concentration of contaminants, including benzo[a]pyrene and Cd. 2+ Each generation increases by 0.8-1.2 mg / L, Pb 2+ The concentration increases by 2.4-2.6 mg / L per generation, while the concentration of methyl parathion increases by 2.8-3.2 mg / L per generation, with a total of 4-6 generations of domestication.

[0007] Preferably, the liquid culture medium, based on water, comprises 18-22 g / L glucose, 8-12 g / L peptone, 4-6 g / L yeast extract, and 8-12 g / L sodium chloride.

[0008] Step 3: After the acclimatization and cultivation are completed, the bacterial solution is centrifuged at 7000-9000 rpm for 8-12 minutes at 3-5℃. The bacterial cells are collected and resuspended in sodium alginate-humic acid solution to achieve a bacterial concentration of (0.8-1.2)×10⁻⁶. 10 The bacterial culture was then mixed with a 0.8-1.2% gelatin solution and stirred at 30-40°C for 3-5 minutes. The mixture was then added to a calcium chloride-chitosan solution at a rate of 4-5% of the total volume per minute and allowed to stand at 3-5°C for 35-45 minutes. The mixture was then filtered to remove the filtrate, yielding microbial capsules.

[0009] Preferably, the volume ratio of the bacterial solution, gelatin solution, and calcium chloride-chitosan solution is 1:(2-4):(15-20).

[0010] Preferably, in the sodium alginate-humic acid solution, based on water, the mass fraction of sodium alginate is 1.8-2.2%, and the mass fraction of humic acid is 0.8-1.2%. In the calcium chloride-chitosan solution, based on water, the mass fraction of calcium chloride is 1.8-2.2%, the mass fraction of chitosan is 0.4-0.6%, and the volume fraction of acetic acid is 1-2%.

[0011] Step 4: Before soil remediation, the soil to be remediated is sampled in a grid pattern, with one sampling point every 80-120 square meters. The characteristic pollutant types and concentrations at the sampling points are analyzed. Based on the type and degree of pollutants, the plot is divided into lightly polluted areas, moderately polluted areas, and heavily polluted areas.

[0012] Preferably, the classification standard is the risk screening value in the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial)" (GB 15618-2018). Areas with a single or compound pollutant concentration in the soil ≤ 1.5 times the risk screening value are lightly polluted areas, areas with a single or compound pollutant concentration in the soil < 1.5 times < 3 times the risk screening value are moderately polluted areas, and areas with a single or compound pollutant concentration in the soil ≥ 3 times the risk screening value are heavily polluted areas.

[0013] Step 5, Week 1 of soil remediation: Deeply till the soil to a depth of 25-30cm, and apply 25-30kg / acre of nutrient solution during tilling. Till evenly and water until the soil moisture content is 70-80%. In the second week of soil remediation, apply 50-80 kg / mu of microbial capsules to lightly polluted areas; apply 80-120 kg / mu of microbial capsules and 40-50 kg / mu of organic-inorganic remediation agent to moderately polluted areas; and apply 200-300 kg / mu of a microbial-composite carrier remediation agent, combining microbial capsules and organic-inorganic remediation agent, to heavily polluted areas. Detect risk screening values ​​for different polluted areas every 80-100 days, reclassify light, moderate, and heavily polluted areas, and apply microbial capsules and remediation agents accordingly.

[0014] Preferably, the nutrient is molasses, fermented soybean meal, diammonium hydrogen phosphate and potassium sulfate, in a mass ratio of (7-9):(10-20):(2-4):(1-3).

[0015] Preferably, the organic-inorganic remediation agent is prepared by mixing chitosan, humic acid, bentonite, hydroxyapatite and 0.4-0.6 g / L glutaraldehyde aqueous solution at a ratio of (25-35) g:(15-25) g:(35-45) g:(8-12) g:(450-550) mL, and stirring at 45-55℃ and 150-200 rpm for 2-3 hours to obtain the organic-inorganic remediation agent.

[0016] Preferably, the preparation method of the microbial-composite carrier repair agent is as follows: microbial capsules, organic-inorganic repair agent and molasses solution with a mass fraction of 4-6% are mixed at a mass ratio of 1:(4-6):(4-6), and shaken at 40-60 rpm for 2-3 hours to obtain the microbial-composite carrier repair agent.

[0017] Step 6: After applying the remediation agent, cover the soil surface with biodegradable black mulch film. Remove the film every 18-22 days and shallowly cultivate the soil to a depth of 5-8 cm. In conjunction with the first removal of the film, apply 100-200 L / mu of compound nutrient solution, and then apply it every 28-32 days thereafter. In the third month of soil remediation, apply 80-120 kg / mu of bio-organic fertilizer, and then apply it every 60-90 days thereafter.

[0018] Preferably, the compound nutrient solution comprises, based on water, 0.4-0.6% urea, 0.2-0.4% potassium dihydrogen phosphate, and 0.04-0.06% magnesium sulfate by mass fraction.

[0019] Preferably, the bio-organic fertilizer comprises well-rotted manure, well-rotted soybean meal, diatomaceous earth, and polyglutamic acid in a mass ratio of (80-120):(8-12):(50-60):(0.2-0.4).

[0020] The present invention has the following advantages: (1) Highly efficient treatment of complex pollution, overcoming the limitations of single-species microbial remediation technologies. Existing microbial remediation technologies mostly use single-species microorganisms, which can only target specific pollutants and cannot effectively treat the complex pollution commonly found in actual soils. This invention uses Bacillus subtilis, Rhodopseudomonas erythrosporum, and Saccharomyces cerevisiae in combination to target organic pollutants (such as benzo[a]pyrene and methyl parathion) and heavy metals (such as Cd) respectively. 2+ and Pb 2+ This multi-species synergistic effect significantly improves remediation efficiency, especially in complex soil environments where multiple pollutants coexist, avoiding the shortcomings of single remediation technologies. Furthermore, it enhances the tolerance and degradation capacity of microorganisms to pollutants through multiple generations of domestication.

[0021] (2) Microbial encapsulation technology enhances environmental adaptability and durability. In traditional microbial remediation, microorganisms are directly exposed to the soil environment, making them susceptible to factors such as temperature, humidity, and competition, resulting in low survival rates and decreased activity. This invention encapsulates microorganisms in sodium alginate-humic acid-gelatin composite capsules, forming a protective microenvironment. This not only improves the stability of the microorganisms but also extends their duration of action in the soil. Encapsulation technology reduces the loss and inactivation of microorganisms, ensuring the continued effectiveness of the remediation agent, thereby improving the overall remediation effect and reducing the frequency and cost of repeated application.

[0022] (3) Precise remediation by zone, optimizing resource utilization. Existing remediation methods often ignore the spatial heterogeneity of soil pollution, leading to inappropriate dosage of remediation agents and waste of resources. This invention uses grid-based sampling and zoning based on pollution level to precisely apply different dosages of microbial capsules and remediation agents according to the type and concentration of pollutants. This zoning management achieves optimized resource allocation, reducing the dosage of remediation agents in lightly polluted areas to save costs, and strengthening remediation efforts in heavily polluted areas to ensure effectiveness, thus improving the targetedness and economy of remediation.

[0023] (4) Integrated soil management promotes ecological restoration. Relying solely on microbial remediation often neglects the overall health of the soil ecosystem. This invention combines the application of nutrients, compound nutrient solutions, and bio-organic fertilizers during the remediation process, providing microorganisms with the necessary nutrients and energy to maintain their metabolic activity. Simultaneously, mulching and regular shallow tillage regulate soil temperature, humidity, and aeration, further optimizing the microbial growth environment. This integrated management not only accelerates pollutant degradation but also improves soil fertility and structure, promoting the long-term stability and restoration of the soil ecosystem.

[0024] 5) Sustainability and environmental friendliness: Compared to chemical remediation methods, this invention is entirely based on biological and natural materials (such as humic acid, chitosan, sodium alginate, etc.), avoiding the risk of secondary pollution. The microbial remediation process is natural and safe, in line with the concept of green and sustainable development. Furthermore, through regular monitoring and dynamic adjustment of the remediation strategy, the scientific rigor and adaptability of the remediation process are ensured, enabling it to cope with changes in soil conditions and achieve long-term remediation goals. Detailed Implementation

[0025] The technical solutions in the embodiments of the invention are described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1 Raw material preparation: Bacillus subtilis powder was purchased from Jinan Xinhe Chemical Technology Co., Ltd., Rhodopseudomonas erythrosporum powder was purchased from Shandong Qilu Chemical Technology Co., Ltd., and Saccharomyces cerevisiae powder was purchased from Shandong Infinida Biotechnology Co., Ltd.

[0027] Liquid culture medium: water-based, consisting of 20 g / L glucose, 10 g / L peptone, 5 g / L yeast extract and 10 g / L sodium chloride.

[0028] Sodium alginate-humic acid solution: Based on water, the mass fraction of sodium alginate is 2% and the mass fraction of humic acid is 1%.

[0029] Calcium chloride-chitosan: Based on water, the mass fraction of calcium chloride is 2%, the mass fraction of chitosan is 0.5%, and the volume fraction of acetic acid is 2%.

[0030] Nutrients: molasses, fermented soybean meal, diammonium hydrogen phosphate and potassium sulfate, in a mass ratio of 8:15:3:2.

[0031] Preparation method of organic-inorganic remediation agent: Chitosan, humic acid, bentonite, hydroxyapatite and 0.5 g / L glutaraldehyde aqueous solution are mixed in a ratio of 30 g: 20 g: 40 g: 10 g: 500 mL and stirred at 50 °C and 180 rpm for 2.5 h to obtain organic-inorganic remediation agent.

[0032] Preparation method of microbial-composite carrier repair agent: Microbial capsules, organic-inorganic repair agent and 5% molasses solution are mixed at a mass ratio of 1:5:5 and shaken at 50 rpm for 2.5 h to obtain microbial-composite carrier repair agent.

[0033] Compound nutrient solution: Based on water, it includes 0.5% urea, 0.3% potassium dihydrogen phosphate, and 0.05% magnesium sulfate by mass.

[0034] Bio-organic fertilizer: well-rotted manure, well-rotted soybean meal, diatomaceous earth and polyglutamic acid, in a mass ratio of 100:10:55:0.3.

[0035] The specific improvement method is as follows: Step 1: Bacillus subtilis, Rhodopseudomonas erythrosporum, and Saccharomyces cerevisiae were inoculated into liquid culture media containing different contaminants and cultured at 30°C and 150 rpm for 48 hours with shaking. The liquid culture medium inoculated with Bacillus subtilis contained 1 mg / L benzo[a]pyrene, the liquid culture medium inoculated with Rhodopseudomonas erythrosporum contained 2 mg / L methyl parathion, and the liquid culture medium inoculated with Saccharomyces cerevisiae contained 2 mg / L Cd. 2+ and 5 mg / L Pb 2+ .

[0036] Step two: After the culture is complete, take 5% of the culture medium and transfer it to a liquid culture medium containing a higher concentration of contaminants, benzo[a]pyrene and Cd. 2+ Each generation increases by 1 mg / L, Pb 2+ The concentration of methyl parathion increased by 2.5 mg / L per generation, and the concentration of methyl parathion increased by 3 mg / L per generation, for a total of 5 generations of domestication.

[0037] Step 3: After the acclimatization culture is completed, the bacterial solution is centrifuged at 8000 rpm for 10 min at 4℃, the bacterial cells are collected, and resuspended in sodium alginate-humic acid solution to make the bacterial concentration 1×10⁻⁶. 10 The bacterial culture was diluted to CFU / mL and then mixed with a 1% gelatin solution. The mixture was stirred at 35°C for 4 min. This mixture was then added to a calcium chloride-chitosan solution at a rate of 4.5% of the total volume per min. The mixture was allowed to stand at 4°C for 40 min, filtered, and the filtrate was removed to obtain microbial capsules. The volume ratio of the bacterial culture, gelatin solution, and calcium chloride-chitosan solution was 1:3:18.

[0038] Step 4: Before soil remediation, the soil to be remediated is sampled in a grid pattern, with one sampling point per 100 square meters. The characteristic pollutant types and concentrations at the sampling points are analyzed. Based on the type and degree of pollutants, the plot is divided into lightly polluted areas, moderately polluted areas, and heavily polluted areas.

[0039] The classification criteria are the risk screening values ​​in the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial)" (GB15618-2018). Areas with a single or compound pollutant concentration in the soil ≤ 1.5 times the risk screening value are lightly polluted areas; areas with a single or compound pollutant concentration in the soil < 1.5 times < 3 times the risk screening value are moderately polluted areas; and areas with a single or compound pollutant concentration in the soil ≥ 3 times the risk screening value are heavily polluted areas.

[0040] Step 5, Week 1 of soil remediation: Deeply till the soil to a depth of 28cm, and apply 28kg / acre of nutrient solution during tilling. Till evenly and water until the soil moisture content reaches 75%. In the second week of soil remediation, 75 kg / mu of microbial capsules were applied to lightly polluted areas; 100 kg / mu of microbial capsules and 45 kg / mu of organic-inorganic remediation agent were applied to moderately polluted areas; and 250 kg / mu of microbial capsules and organic-inorganic remediation agent were combined into a microbial-composite carrier remediation agent for heavily polluted areas. Risk screening values ​​for different polluted areas were tested every 90 days, and the light, moderate and heavy polluted areas were reclassified and microbial capsules and remediation agents were applied.

[0041] Step 6: After applying the remediation agent, cover the soil surface with biodegradable black mulch film. Remove the film every 21 days and shallowly cultivate the soil to a depth of 7cm. In conjunction with the first removal of the film, apply 150L / mu of compound nutrient solution, and then apply it every 30 days thereafter. In the third month of soil remediation, apply 100kg / mu of bio-organic fertilizer, and then apply it every 60-90 days thereafter.

[0042] Experimental Example 1 A contaminated farmland soil sample of approximately 1 acre was selected. The main pollutants included benzo[a]pyrene, methyl parathion, DDT, petroleum hydrocarbons, Cd, Pb, Cr, and As. The soil texture was loam, with a pH of 6.5-7.5. Sampling was conducted using a grid method, with one sampling point per 100 square meters, for a total of 7 sampling points: 3 lightly contaminated areas, 3 moderately contaminated areas, and 1 heavily contaminated area. The method described in Example 1 was used to remediate the contaminated soil. Sampling and analysis were performed every 90 days, with 3 replicates. The results are shown in Table 1. Heavy metals (Cd, Pb, Cr, As) were determined by atomic absorption spectrometry (AAS), and organic pollutants were determined by gas chromatography-mass spectrometry (GC-MS).

[0043] Table 1. Changes in the concentration of various pollutants in different contaminated areas before and after remediation (mg / kg)

[0044] As shown in Table 1, after a 180-day remediation period, the concentrations of all pollutants (including organic pollutants benzo[a]pyrene, methyl parathion, DDT, and heavy metals Cd, Pb, Cr, and As) in different pollution areas decreased significantly, with removal rates all exceeding 64.4%. This demonstrates that the microbial composite remediation system provided by this invention can effectively address complex composite pollution scenarios. A horizontal comparison of the data shows that for the same pollutant, the removal rate is typically highest in heavily polluted areas. For example, the removal rates of DDT in lightly, moderately, and heavily polluted areas were 71.4%, 78.6%, and 80.0%, respectively. This proves that the zoned precise remediation strategy adopted in this invention is scientific and effective, achieving optimized resource allocation and maximizing remediation effects by introducing a stronger remediation agent (microbial-composite carrier remediation agent) in more severely polluted areas. This method not only achieves a removal rate of over 70% for organophosphate pesticides such as methyl parathion and DDT, and polycyclic aromatic hydrocarbons such as benzo[a]pyrene, but also demonstrates excellent performance (removal rates of 64.4%-79.1%) for various heavy metals such as Cd, Pb, Cr, and As. This overcomes the limitations of single-strain or single-technology methods that can only treat specific types of pollutants, highlighting the technical advantages of multi-strain synergy and the combined use of organic-inorganic remediation agents. Comparing data from 90 and 180 days of remediation, the concentrations of all pollutants further decreased significantly after 180 days. This indicates that this remediation method has a sustained effect; the microorganisms can maintain activity in the soil for a longer period, continuously degrading pollutants or altering their form, rather than being a one-off, short-term reaction.

[0045] After 180 days of remediation, the concentrations of most pollutants in the lightly polluted areas have fallen below or approached the risk screening values ​​in the "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control (Trial)" (GB 15618-2018). Pollutant concentrations in the moderately and heavily polluted areas have also been significantly reduced, and environmental risks and ecological hazards have been substantially decreased, demonstrating the important application value of this method in ensuring agricultural product safety and soil health.

[0046] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for remediating contaminated arable land soil based on microorganisms, characterized in that, Includes the following steps: Step 1: Bacillus subtilis, Rhodopseudomonas erythrosporum, and Saccharomyces cerevisiae were inoculated separately into liquid culture media containing different contaminants and cultured with shaking. Specifically, the liquid culture medium inoculated with Bacillus subtilis contained 0.8-1.2 mg / L benzo[a]pyrene, the liquid culture medium inoculated with Rhodopseudomonas erythrosporum contained 1.8-2.2 mg / L methyl parathion, and the liquid culture medium inoculated with Saccharomyces cerevisiae contained 1.8-2.2 mg / L Cd. 2+ and 4.5-5.5 mg / L Pb 2+ ; Step two: After culturing, take 4-6% of the culture medium and transfer it to a liquid culture medium containing a higher concentration of contaminants, including benzo[a]pyrene and Cd. 2+ Each generation increases by 0.8-1.2 mg / L, Pb 2+ The concentration increases by 2.4-2.6 mg / L per generation, and the concentration of methyl parathion increases by 2.8-3.2 mg / L per generation, with a total of 4-6 generations of domestication. Step 3: After the acclimatization and cultivation are completed, the bacterial cells are collected by centrifugation and resuspended in sodium alginate-humic acid solution to achieve a bacterial concentration of (0.8-1.2)×10⁻⁶. 10 CFU / mL, then mix this bacterial solution with gelatin solution and stir, then add this mixed solution to calcium chloride-chitosan solution at a rate of 4-5% total volume / min, let stand, filter, remove the filtrate, and obtain microbial capsules; the volume ratio of the bacterial solution, gelatin solution and calcium chloride-chitosan solution is 1:(2-4):(15-20); Step 4: Before soil remediation, grid sampling is carried out on the soil to be remediated. The types and concentrations of characteristic pollutants at the sampling points are analyzed. Based on the type and degree of pollutants, the plot is divided into lightly polluted areas, moderately polluted areas, and heavily polluted areas. Step 5, Week 1 of soil remediation: Deeply till the soil to a depth of 25-30cm, and apply 25-30kg / acre of nutrient solution during tilling. Till evenly and water until the soil moisture content is 70-80%. In the second week of soil remediation, apply 50-80 kg / mu of microbial capsules to lightly polluted areas; apply 80-120 kg / mu of microbial capsules and 40-50 kg / mu of organic-inorganic remediation agent to moderately polluted areas; and apply 200-300 kg / mu of a microbial-composite carrier remediation agent, combining microbial capsules and organic-inorganic remediation agent. Detect risk screening values ​​for different polluted areas every 80-100 days, reclassify light, moderate, and heavy polluted areas, and apply microbial capsules and remediation agents accordingly. Step 6: After applying the remediation agent, cover the soil surface with biodegradable black mulch film. Remove the film every 18-22 days and shallowly cultivate the soil to a depth of 5-8 cm. In conjunction with the first removal of the film, apply 100-200 L / mu of compound nutrient solution, and then apply it every 28-32 days thereafter. In the third month of soil remediation, apply 80-120 kg / mu of bio-organic fertilizer, and then apply it every 60-90 days thereafter.

2. The method for remediating contaminated farmland soil based on microorganisms according to claim 1, characterized in that, The liquid culture medium described in steps one and two, based on water, comprises 18-22 g / L glucose, 8-12 g / L peptone, 4-6 g / L yeast extract, and 8-12 g / L sodium chloride.

3. The method for remediating contaminated farmland soil based on microorganisms according to claim 1, characterized in that, In step three, the sodium alginate-humic acid solution contains 1.8-2.2% sodium alginate and 0.8-1.2% humic acid, with water as the reference.

4. The method for remediating contaminated farmland soil based on microorganisms according to claim 1, characterized in that, In step three, the calcium chloride-chitosan mixture is based on water, with a calcium chloride mass fraction of 1.8-2.2%, a chitosan mass fraction of 0.4-0.6%, and an acetic acid volume fraction of 1-2%.

5. The method for remediating contaminated farmland soil based on microorganisms according to claim 1, characterized in that, The classification criteria mentioned in step four are the risk screening values ​​in the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial)" (GB 15618-2018). Areas with a single or compound pollutant concentration in the soil ≤ 1.5 times the risk screening value are lightly polluted areas; areas with a single or compound pollutant concentration in the soil < 1.5 times < 3 times the risk screening value are moderately polluted areas; and areas with a single or compound pollutant concentration in the soil ≥ 3 times the risk screening value are heavily polluted areas.

6. The method for remediating contaminated farmland soil based on microorganisms according to claim 1, characterized in that, The nutrients mentioned in step five are molasses, fermented soybean meal, diammonium hydrogen phosphate and potassium sulfate, in a mass ratio of (7-9):(10-20):(2-4):(1-3).

7. The method for remediating contaminated farmland soil based on microorganisms according to claim 1, characterized in that, The preparation method of the organic-inorganic remediation agent in step five is as follows: chitosan, humic acid, bentonite, hydroxyapatite and 0.4-0.6 g / L glutaraldehyde aqueous solution are mixed at (25-35) g:(15-25) g:(35-45) g:(8-12) g:(450-550) mL and stirred at 45-55℃ and 150-200 rpm for 2-3 h to obtain the organic-inorganic remediation agent.

8. The method for remediating contaminated farmland soil based on microorganisms according to claim 1, characterized in that, The preparation method of the microbial-composite carrier repair agent in step five is as follows: microbial capsules, organic-inorganic repair agent and molasses solution with a mass fraction of 4-6% are mixed at a mass ratio of 1:(4-6):(4-6), and shaken at 40-60 rpm for 2-3 hours to obtain the microbial-composite carrier repair agent.

9. A method for remediating contaminated farmland soil based on microorganisms according to claim 1, characterized in that, The compound nutrient solution mentioned in step six, based on water, includes 0.4-0.6% urea, 0.2-0.4% potassium dihydrogen phosphate, and 0.04-0.06% magnesium sulfate by mass.

10. A method for remediating contaminated farmland soil based on microorganisms according to claim 1, characterized in that, The bio-organic fertilizer mentioned in step six includes well-rotted manure, well-rotted soybean meal, diatomaceous earth, and polyglutamic acid, with a mass ratio of (80-120):(8-12):(50-60):(0.2-0.4).

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