Preparation method of microorganism combined modifier for repairing cadmium-polluted rice soil

Abstract

The invention provides a preparation method of a microbial combined modifier for cadmium-polluted rice soil remediation, which comprises the following steps: carrying out swelling treatment on a porous carrier material, and carrying out attenuation or disinfection treatment by using growth promoting liquid; the growth promoting liquid is a root exudate solution of cynodon dactylon, rice, ryegrass or rape; adding a porous carrier material and a growth promoting solution into the aspergillus aculeatus solution, and oscillating to obtain a mixed solution; and mixing the mixed solution with sodium alginate, and carrying out gelation treatment to obtain the microorganism combined modifier. The microorganism combined modifier overcomes the defects of biotoxicity, agglomeration and the like of a porous carrier material, solves the problems of low survival rate, poor tolerance and the like in a functional microorganism repairing process, increases the content of crop rhizosphere microorganism source growth-promoting hormone, effectively promotes the yield and stress resistance of rice, and improves the quality of the rice. Meanwhile, migration and bioavailability of rice rhizosphere heavy metal are effectively reduced, and absorption of rice to heavy metal such as cadmium is inhibited.

Claims

1. A method for preparing a microbial combined modifier for remediation of cadmium-contaminated paddy soil, characterized in that: The following steps are involved: The first step is to prepare a porous carrier material; The second step is to expand the porous carrier material and perform a toxic reduction or disinfection treatment using a growth-promoting liquid; the growth-promoting liquid is a solution of root secretions of Bermuda grass, rice, ryegrass or rapeseed; Step 3: prepare Aspergillus aculeatus solution; Step 4: Add a porous carrier material to the Aspergillus aculeatus solution at a ratio of 1 g of the porous carrier material to the volume of the Aspergillus aculeatus solution of 10-60 ml. After mixing, add a certain amount of growth-promoting liquid, and shake at 25-30° C. for 2-36 hours to obtain a mixed solution. Step 5: Mix the mixed liquid with sodium alginate and perform gelation treatment to obtain a microbial combined improver.

2. The method for preparing a microbial combined modifier for remediation of cadmium-contaminated paddy soil according to claim 1, characterized in that: The porous carrier material is one or more of graphene oxide, MOF sponge material, COF material, carbon nanotube, chitosan, boron nitride nanosheet, and porous organic polymer.

3. The method for preparing a microbial combined modifier for remediation of cadmium-contaminated paddy soil according to claim 2, characterized in that: The preparation method of the graphene oxide is as follows: using biomass as a carbon source and hydrogen peroxide as an oxidant, graphene oxide is prepared by a hydrothermal reaction, the reaction temperature is 200-250°C, the reaction time is 10-15 hours, and the biomass is one or more of glucose, sucrose, starch, and cellulose.

4. The method for preparing a microbial combined modifier for remediation of cadmium-contaminated paddy soil according to claim 1, characterized in that: In the second step, the porous carrier material after thermal expansion treatment is dispersed in deionized water, the pH value is adjusted to alkaline, and a growth-promoting liquid is added. The ratio of the volume of the growth-promoting liquid added to the mass of the porous carrier material is (10-30) ml: 1 g. The reaction is carried out under room temperature with magnetic stirring at 60-120 rpm for 1-6 hours, and the reaction is centrifuged at 8000-9000 rpm, washed, and dried to obtain a modified carrier material.

5. The method for preparing a microbial combined modifier for remediation of cadmium-contaminated paddy soil according to claim 4, characterized in that: The pH value is 8-9; the ratio of the volume of the growth-promoting liquid added to the mass of the porous carrier material is (15-20) ml:1 g; and the magnetic stirring time is 2-3 hours.

6. The method for preparing a microbial combined modifier for remediation of cadmium-contaminated paddy soil according to claim 1, 4 or 5, characterized in that: The preparation method of the growth-promoting liquid is as follows: First, in spring, select dry and barren soil for Bermudagrass cultivation, and in summer, collect the Bermudagrass root system for exudates, or select rice at the heading stage and dig out the complete rice root system; Secondly, after washing the roots clean, use mercuric chloride solution to rinse the root surface for sterilization; Again, the roots were transferred to ultrapure water and placed under strong sunlight for a period of time to collect the secretions; Then, the roots are collected, cut into pieces, ground, and placed in 50ml-100ml of 5%-10% ethanol solution to allow the extract to be fully mixed with the root secretions. After extraction at 25℃-28℃ for 24 hours, centrifugation and filtration are performed. Finally, the filtrate is freeze-dried and stored at ultra-low temperature. When used, 1-3 g of frozen powder is dissolved in 5-10 ml of 3% potassium dihydrogen phosphate to obtain a growth-promoting solution.

7. The method for preparing a microbial combined modifier for remediation of cadmium-contaminated paddy soil according to claim 1, characterized in that: In the third step, Aspergillus aculeatus was extracted from the rhizosphere soil of the plant and cultured and activated to obtain an Aspergillus aculeatus solution. The concentration of Aspergillus aculeatus in the culture medium after extraction and culture was 8.79×10 7 -6.73×10 9 pieces / mL.

8. The method for preparing a microbial combined modifier for remediation of cadmium-contaminated paddy soil according to claim 7, characterized in that: The plant is one or more of bermudagrass, rapeseed, ryegrass, and rice; the effective content of heavy metal cadmium in the rhizosphere soil of the plant is 0.5-2 mg / kg; the extracted Aspergillus aculeatus is activated by solid culture medium and propagated by liquid culture medium, and the end point of the liquid culture medium diffusion culture is OD 600 The value reaches 1.0-4.

0.

9. The method for preparing a microbial combined modifier for remediation of cadmium-contaminated paddy soil according to claim 1, characterized in that: In the fourth step, the ratio of the mass of the carrier material added to the volume of the Aspergillus aculeatus solution is 1g:(20-40)ml; the amount of the growth-promoting liquid added is 2-4mL; the Aspergillus aculeatus solution and the modified porous carrier material are mixed and shaken in a shaker at a temperature of 28-30°C for 12-24 hours; in the fifth step, the mixed solution obtained by the shaking culture is mixed with an equal volume of sodium alginate solution, and then a sterile CaCl2 solution with a mass volume percentage of 4% is added dropwise. After the mixed solution is completely gelled, it is washed 3-5 times with sterile saline with a mass volume percentage of 0.85% to obtain a microbial combined modifier; the mass percentage concentration of the sodium alginate solution is 2%-6%.

10. A method for using the microbial combined improver prepared according to any one of claims 1 to 9, characterized in that: The following steps are involved: The microbial combined amendment is added to the crop rhizosphere soil at a mass ratio of 1:(10-15) for activation culture. The moisture of the crop rhizosphere soil is 50%-70%, and the activation culture temperature is 25-28°C. After culturing for 5-7 days, the crop rhizosphere soil mixed with the microbial combined amendment is applied to the cadmium-contaminated soil. The application amount is calculated based on the actual application amount of the microbial combined improver, which is 0.05%-0.1%.

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