Method for removing cadmium pollution of rice field soil

Abstract

The invention relates to the technical field of environment, and discloses a method for removing cadmium pollution in rice field soil, which is characterized by comprising the following steps: adding a compound microbial agent into the rice field soil, then continuously flooding and adding sodium thiosulfate for treatment. The method is characterized in that an application microbial agent comprises the following components: Ytrophobacteroides L85, streptomyces albidus R92, Acidithiobacillus ferrooxidans W85, and bacillus licheniformis S91. The application microbial agent comprises the following components: the Ytrophobacteroides L85, the streptomyces albidus R92, the Acidithiobacillus ferrooxidans W85, and the bacillus licheniformis S91. The compound microbial agent can rapidly grow and breed in the rice field soil, can fix free cadmium in the rice field soil in various forms such as direct adsorption, soil pH adjustment, oxidation reduction and sulfide precipitate formation, and can fix and passivate cadmium. The method can remove the heavy metal cadmium in the soil, is convenient to implement and low in cost, and has very good popularization and application values.

Description

Technical Field

[0001] The invention relates to the field of environmental technology, and in particular to a method for removing cadmium pollution from paddy field soil. Background Art

[0002] In recent years, due to the irrational use of chemical fertilizers and improper high-intensity planting management, the soil quality problems in my country's main grain-producing areas have become increasingly serious, especially the intensification of heavy metal pollution. The application of large amounts of chemical fertilizers has not brought about a significant increase in grain yields, but has led to a decrease in soil organic matter content and a continuous decline in farmland fertility.

[0003] Cadmium exposure is a serious hazard to human health, especially its long-term toxicity to the kidneys, liver, and central nervous system. After chronic cadmium exposure enters the human body through food, water, and air, it accumulates in the liver and kidneys, increasing the risk of cancer and osteoporosis and impairing the function of these organs. Cadmium can also cause neurotoxicity through oxidative stress and mitochondrial dysfunction, manifesting as cognitive impairment and behavioral abnormalities, especially affecting children, pregnant women, and the elderly. Reducing cadmium exposure in the environment and taking measures such as nutritional intervention are key strategies for preventing and controlling cadmium toxicity.

[0004] By adjusting the soil pH and managing water content, the bioavailability of cadmium can be reduced and its migration in rice can be reduced. In addition, the use of bioremediation methods, such as the use of microbial agents to passivate free cadmium, can significantly reduce the content of free cadmium in the soil and reduce its absorption in rice. By optimizing farmland management strategies and taking effective soil remediation measures, soil heavy metal pollution can be reduced while improving soil safety and agricultural product quality. Although existing technologies can reduce cadmium metal in the soil, the effect is still not significant. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for removing cadmium pollution in paddy field soil, which can remove the heavy metal cadmium content in the soil.

[0006] The present invention provides a method for removing cadmium pollution from paddy soil, comprising the following steps: Composite microbial remediation agents were added to paddy field soil, which was then treated by continuous flooding and addition of sodium thiosulfate.

[0007] Furthermore, the composite microbial remediation agent is composed of Yntrophobacteraceae L85 , Streptomyces parvum R92, Acidithiobacillus ferrooxidans W85 , Bacillus licheniformis S91.

[0008] Further, by mass, the Yntrophobacteraceae L85 , Streptomyces parvum R92, Acidithiobacillus ferrooxidans W85 , and Bacillus licheniformis S91 is 1:1:1:1.

[0009] Furthermore, the added mass fraction of the composite microbial remediation agent in paddy field soil is 50-70 kg / mu.

[0010] Furthermore, the specific process of the flooding includes: the water level is 5-12 cm higher than the paddy field soil, and the flooding lasts 7-14 days.

[0011] Furthermore, the added mass of the sodium thiosulfate is 1-5 kg / mu.

[0012] The embodiments of the present invention have the following technical effects: The method of the present invention can successfully remove cadmium pollution in paddy field soil. The composite microbial remediation agent of the present invention can grow and reproduce rapidly in paddy field soil, and can fix free cadmium in paddy field soil by direct adsorption, soil pH adjustment, oxidation-reduction, and formation of sulfide precipitation, thereby fixing and passivating cadmium. The present invention is easy to implement, low in cost, and has great value for popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 It is a data diagram of cadmium content in paddy field soil of the embodiments of the present invention and the comparative example. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0015] In a first aspect, some embodiments of the present invention provide a method for removing cadmium pollution from paddy soil, comprising the following steps: Composite microbial remediation agents were added to paddy field soil, which was then treated by continuous flooding and addition of sodium thiosulfate.

[0016] In some embodiments, the composite microbial agent is composed of Yntrophobacteraceae L85 , Streptomyces parvum R92, Acidithiobacillus ferrooxidans W85 , Bacillus licheniformis S91.

[0017] In some embodiments, by mass, the Yntrophobacteraceae L85 , Streptomyces parvum R92, Acidithiobacillus ferrooxidans W85 , and Bacillus licheniformis S91 is 1:1:1:1.

[0018] In some embodiments, the mass fraction of the composite microbial agent added to paddy field soil is 50-70 kg / mu.

[0019] In some embodiments, the specific process of flooding includes: the water level is 5-12 cm higher than the paddy field soil, and the flooding lasts 7-14 days.

[0020] In some embodiments, the added mass of sodium thiosulfate is 1-5 kg / mu.

[0021] The following is described in conjunction with some specific embodiments: Embodiment 1: Bacteria: Yntrophobacteraceae L85, culture medium: 5.0g yeast extract, 5.0g glucose, 1.0g potassium nitrate, 1.0g potassium dihydrogen phosphate, 1.0g magnesium sulfate, 0.2g calcium chloride, 1000mL distilled water, pH 7.2-7.4. Culture method: slant culture Yntrophobacteraceae Two loops of L85 strain were inoculated into 100 mL of liquid culture medium and cultured in a shaker at 30°C and 100 rpm for 2-3 days. Then, the inoculation volume was transferred to fresh culture medium at 10% (v / v) and cultured for 48 hours. The effective bacterial count was finally 1.0-2.0×10 9 cfu / mL.

[0022] Embodiment 2: Bacterial strain: Streptomyces parvum R92, culture medium: peptone 5.0g, beef extract 3.0g, yeast extract 1.0g, distilled water 1000mL, pH 7.0-7.2. Culture method: Inoculate 2 loops of Streptomyces parvum R92 slant culture into 100mL liquid culture medium, shake culture at 28°C, 120rpm for 2-3 days, then transfer to fresh culture medium at 10% (v / v) inoculation volume, and continue to culture for 48 hours. The final effective bacterial count is 3.0-5.0×10 9 cfu / mL.

[0023] Embodiment 3: Bacteria: Acidithiobacillus ferrooxidansW85 medium: 9K medium (containing Fe²⁺ as an oxidation substrate), pH 2.0-2.5, 1000mL of distilled water. Culture method: Inoculate the strain into 100mL of 9K liquid medium and culture it at 30°C for 5-7 days to promote oxidative metabolism. After cultivation, the bacterial density reaches the optimal state and the bacterial activity is high.

[0024] Embodiment 4: Bacterial strain: Bacillus licheniformis S91, culture medium: 5.0g peptone, 3.0g beef extract, 1.0g magnesium sulfate, 0.2g calcium chloride, 1000mL distilled water, pH 7.0-7.2. Culture method: Inoculate 2 loops of Bacillus licheniformis S91 into 100mL liquid culture medium, shake and culture at 30°C, 100rpm for 2 days. Then transfer to new culture medium at 10% (v / v) inoculation volume, continue to culture for 48 hours, and obtain an effective bacterial count of 1.0-5.0×10 9 cfu / mL.

[0025] Embodiment 5: a) Take Yntrophobacteraceae L85 10 parts, Streptomyces parvum R92 10 parts, Acidithiobacillus ferrooxidans 10 parts of W85 and 10 parts of Bacillus licheniformis S91 are mixed in a ratio of 10:10:10:10 to form a composite microbial remediation agent. At the same time, add appropriate amounts of nutrients such as dipotassium hydrogen phosphate, ammonium chloride, magnesium sulfate, and sodium lactate to ensure the activity and metabolic needs of microorganisms in the soil environment. Mix the above ingredients evenly and add 300 parts of biochar as a carrier to improve the stability and adsorption capacity of microorganisms in the soil. Crush the mixture to a fineness of 200-250 mesh to ensure the uniformity of the mixture and good application effect.

[0026] b) Take water of the same mass as the mixture obtained in step a), heat it to 45°C, add the mixture into the warm water, and stir it at a constant temperature for 30-50 minutes to fully dissolve the bacterial agent and nutrients to form a highly active bacterial agent solution.

[0027] c) putting the bacterial solution obtained in step b) into a fermentation tank and fermenting and culturing at 25° C. for 10 days. During the fermentation process, no bubbles are generated in the tank to ensure that the microorganisms reach a high density and high activity state during the fermentation process, and finally obtaining a bacterial agent mother solution.

[0028] d) adding the bacterial agent mother solution obtained in step c) to the carrier material at a ratio of 1:0.85 to carry out secondary fermentation to further increase the number and activity of the microorganisms.

[0029] e) Apply d) evenly to the cadmium-contaminated soil at a rate of 50-70 kg per mu, and flood the soil with water at a level of 5-12 cm for 7-14 days to optimize the soil's redox conditions and reduce the bioavailability of cadmium.

[0030] f) On the 5th day of flooding treatment, 1-2 kg of sodium thiosulfate (Na2S2O3) was applied per mu of soil to further complex the cadmium in the soil and enhance its precipitation effect.

[0031] Embodiment 6: Take 30 parts of silicate bacteria, 40 parts of organic matter decomposition bacteria, and 13 parts of bioremediation bacteria and mix them evenly with the culture medium, and then crush them to a fineness of 200-250 mesh, ensuring that the culture medium is twice the total mass of the bacteria and the carrier, and accounts for 8% of the total mass of the mixture; b) taking water of equal mass to the mixture obtained in step a), heating it to 45°C, adding the strain prepared in step a), and stirring at a constant temperature for 30-50 minutes until it is evenly dissolved; c) placing the bacterial solution obtained in step b) into a fermentation tank and fermenting at 25° C. for 10 days until no bubbles are generated in the fermentation tank, thereby obtaining a high-activity, high-density bacterial agent mother solution; d) taking 85% of the mass of the carrier material of the bacterial agent mother solution obtained in step c), mixing it with the bacterial agent mother solution obtained in step c), and performing a secondary expanded fermentation; e) applying the fermented bacterial agent prepared in step d) evenly to the paddy field at a dosage of 50-70 kg per mu, and flooding the paddy field with the water level maintained at 5-12 cm for 7-14 days to optimize the redox conditions of the soil; f) On the fifth day after flooding, 1-2 kg of sodium thiosulfate (Na2S2O3) was applied per mu of paddy field to enhance the complexation and precipitation of cadmium and further reduce the bioavailability of cadmium; g) After completing the flooding and sodium thiosulfate passivation treatment, drain the water and keep the soil moderately moist. Through the above steps, the cadmium in the paddy soil is effectively passivated, which significantly reduces the absorption of cadmium by rice and ensures the safety and quality of rice.

[0032] Example 7: Experimental design for remediation of cadmium-contaminated soil Experimental method: The prepared microbial remediation agent was added to the cadmium-contaminated soil samples at a ratio of 1%, 5%, and 10%, and a control group without the addition of the remediation agent was set up. Each group of samples was cultured at room temperature and kept moderately moist. Samples were taken in the first, second, and fourth weeks, and the residual cadmium content in the soil was detected by ICP-MS to evaluate the effect of the remediation agent on cadmium removal. At the same time, the soil pH, organic matter content, and microbial community diversity were tested to further analyze the mechanism of action of the remediation agent.

[0033] It should be noted that the terms used in the present invention are only for describing specific embodiments, rather than limiting the scope of the present application. As shown in the present specification, unless the context clearly indicates an exception, the words "one", "a", "a kind of" and / or "the" do not specifically refer to the singular, but may also include the plural. The terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method or device. In the absence of more restrictions, the elements defined by the sentence "include one..." do not exclude the presence of other identical elements in the process, method or device including the elements.

[0034] It should also be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. Unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", etc. should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A method for removing cadmium from paddy soil, characterized in that: The steps include: Composite microbial remediation agents were added to paddy field soil, which was then treated by continuous flooding and addition of sodium thiosulfate.

2. The method according to claim 1, characterized in that The composite microbial repair agent is composed of Yntrophobacteraceae L85 , Streptomyces parvum R92, Acidithiobacillus ferrooxidans W85 , Bacillus licheniformis S91.

3. The method according to claim 2, characterized in that In terms of mass, Yntrophobacteraceae L85 , Streptomyces parvum R92, Acidithiobacillus ferrooxidans W85 , and Bacillus licheniformis S91 is 1:1:1:

1.

4. The method according to claim 1, characterized in that The added mass fraction of the composite microbial remediation agent in paddy field soil is 50-70 kg / mu.

5. The method according to claim 1, characterized in that The specific process of the flooding includes: the water level is 5-12 cm higher than the paddy field soil, and the flooding lasts 7-14 days.

6. The method according to claim 1, characterized in that The added mass of the sodium thiosulfate is 1-5 kg / mu.

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