Seed coating material for soil restoration, seed gel ball, preparation method and application thereof

Abstract

The present invention belongs to the field of soil remediation, and discloses a seed coating material and a seed gel ball. The seed coating material includes calcium alginate gel and modified hemp fiber doped in the calcium alginate gel; microorganisms are loaded on the modified hemp fiber and in the calcium alginate gel. The seed gel ball includes plant seeds, and the above-mentioned seed coating material wrapped outside the plant seeds. The present invention increases the microbial load and its activity inside the gel ball by adsorbing microorganisms on modified hemp fiber and then embedding and cross-linking, thereby increasing the seed germination rate, germination potential and microbial survival rate, and can maintain seed vitality and bacterial flora activity for a long time, and the modified hemp fiber plays a role in maintaining the mechanical strength of the gel ball structure, keeping the gel ball from being destroyed, and the product structure is stable. It has a good remediation effect on organically contaminated soil.

Description

Technical Field

[0001] The invention belongs to the technical field of restoration of soil contaminated by organic matter, and in particular relates to seed coating materials, gel balls for soil restoration, and preparation methods and applications thereof. Background Art

[0002] The rapid advancement of my country's urbanization process has accelerated the upgrading of urban industrial structure and the optimization of layout, causing industrial enterprises originally located in the main urban area to relocate outside the city. The organic pollutants such as petroleum hydrocarbons, halogenated hydrocarbons, and polycyclic aromatic hydrocarbons remaining in the soil of industrial sites left behind by factory relocation pose huge environmental risks to surrounding residents. The remediation of soil and environmental safety utilization of contaminated sites have now become a major environmental issue that has attracted much attention from the government and the general public. Studies have shown that the plant-microorganism joint remediation system can promote the rapid degradation and transformation of organic pollutants. For example, the use of plants and specialized microorganisms can effectively remove pollutants such as polycyclic aromatic hydrocarbons in the soil, and the inoculation of mycorrhizal fungi can increase the degradation of polycyclic aromatic hydrocarbons by plants.

[0003] In the actual remediation process, due to the stress of pollutants and indigenous microorganisms in the soil, the germination rate of plant seeds is low and the degrading bacteria are easily inactivated, resulting in poor remediation effects and poor efficiency of plant-microorganism synergistic remediation.

[0004] CN116116894 A discloses a composite seed carrier, which uses white stone, rainbow stone, volcanic rock, ceramsite, perlite, etc. as inorganic carriers, sodium alginate, polyvinyl alcohol, sodium carboxymethyl cellulose, K-carrageenan, gellan gum, plant gel, chitosan, gum arabic, etc. as organic carriers, and the organic carrier and inorganic carrier are placed in a mixture of sodium alginate and microorganisms, and then plant seeds are added, and calcium chloride is added dropwise after stirring evenly, and the composite seed carrier is obtained after freeze drying. The use of organic carriers such as plant gel can make up for the weak mechanical strength of sodium alginate, and the obtained seed carrier can well remove pollutants in the soil. In this scheme, whether vermiculite or volcanic rock is used, the germination rate of the composite seed carrier is lower than that of naked seeds. The germination rate of rainbow stone as an inorganic carrier is not significantly different from that of naked seeds, but its addition amount in the raw material reaches 1%-4%.

[0005] In order to further reduce costs, it is necessary to improve the existing technology, select different materials as seed coatings, and prepare composite seed gel balls for soil remediation. It is also necessary to improve the seed germination rate, increase the microbial load, and improve the mechanical strength of the gel balls while reducing the amount of organic and inorganic carriers to reduce costs and meet usage requirements. Summary of the invention

[0006] The purpose of the present invention is to solve the problems existing in the prior art, and to provide a seed coating material for soil remediation, a seed gel ball, and a preparation method and application thereof. The obtained gel ball can utilize the synergistic symbiosis of plants and microorganisms to degrade pollutants in the soil, thereby improving the degradation efficiency of organic pollutants in the soil; the gel ball product has a stable structure and can maintain seed vitality and bacterial activity for a long time in the complex environment inside the soil.

[0007] The technical solution of the present invention is a seed coating material for soil remediation, comprising calcium alginate gel and modified hemp fiber doped in the calcium alginate gel; microorganisms are loaded on the modified hemp fiber and in the calcium alginate gel.

[0008] The modified hemp fiber is hemp fiber that has been subjected to acid modification or alkali modification.

[0009] Preferably, the microorganism is a petroleum hydrocarbon degrading bacterium.

[0010] The petroleum hydrocarbon degrading bacteria are microorganisms with the function of degrading petroleum hydrocarbon compounds. Preferably, they are selected from Pseudomonas, Achromobacter, Arthrobacter, Micrococcus, Nocardia, Acinetobacter, Brevibacterium, Corynebacterium, Flavobacterium, and fungi include Candida, Rhodotorula, Sporangiophora or Mycobacterium. In a preferred embodiment of the present invention, the petroleum hydrocarbon degrading bacteria are Acinetobacter junii.

[0011] The second embodiment of the present invention is a seed gel ball for soil repair, comprising plant seeds and the above-mentioned seed coating material wrapped around the plant seeds.

[0012] The number of plant seeds encapsulated in the seed gel ball is at least one.

[0013] In one embodiment of the present invention, the plant seeds are rapeseed seeds.

[0014] The seed coating material or seed gel ball can be used to repair soil, especially to repair soil contaminated by organic matter, such as petroleum hydrocarbons.

[0015] The preparation method of the seed gel ball comprises the following steps:

[0016] (1) The modified hemp fiber treated with acid or alkali is mixed with a microbial solution, and after shaking culture, a modified hemp fiber loaded with microorganisms is obtained;

[0017] (2) mixing the modified hemp fiber loaded with microorganisms, plant seeds, sodium alginate solution and microbial culture liquid;

[0018] (3) Add a crosslinking agent solution dropwise to the mixed solution obtained in step (2) to obtain seed gel spheres.

[0019] The OD of the microbial solution in step (1) 600 is 1-2, preferably 1.2-1.6; the mass volume ratio of the modified hemp fiber to the microbial liquid is 1g:10-50mL.

[0020] In step (1), the modified hemp fiber is cultured in a microbial culture solution under shaking for 3-12 hours.

[0021] The modified hemp fiber preparation method comprises the following steps: the hemp fiber is cleaned and dried, chopped into pieces of 0.5-1 mm, and passed through a 60-100 mesh sieve; the sieved hemp fiber is immersed in a 0.4-4 mol / L sodium hydroxide solution or a hydrochloric acid solution, with a solid-liquid mass volume ratio of 1 g:3-10 mL; after shaking culture for 3-24 hours, the fiber is washed to neutrality to obtain alkali-modified hemp fiber or acid-modified hemp fiber.

[0022] Preferably, the hemp fiber is jute fiber.

[0023] In the mixed solution obtained in step (2), the content of modified hemp fiber is 3-15 g / L, and the content of sodium alginate is 10-35 g / L. Preferably, the content of modified hemp fiber is 5-10 g / L, and the content of sodium alginate is 12-30 g / L.

[0024] The OD of the microbial solution in step (2) 600 The volume ratio of the microbial liquid to the sodium alginate solution is 1:5-20, preferably 1:8-15.

[0025] The cross-linking agent is calcium chloride or calcium citrate, and the concentration of the cross-linking agent solution is 20-55 g / L, preferably 30-50 g / L.

[0026] The obtained gel balls for soil repair have a particle size of 3-8 mm, preferably 4-6 mm.

[0027] The present invention has the beneficial effects:

[0028] (1) This technical solution uses sodium alginate and a cross-linking agent to form a gel, which combines plant seeds and microorganisms together, and uses the synergistic restoration of plants and microorganisms to improve the restoration efficiency. The degradation rate of organic matter in contaminated soil reaches more than 50% within 60 days, while protecting plant seeds and bacterial communities from direct impacts of complex factors in the external soil;

[0029] (2) The modified hemp fiber absorbs microorganisms and then embeds and cross-links them, thereby increasing the microbial loading and activity inside the gel ball. The pores of the modified hemp fiber carrier material provide a buffer for the proliferation of microorganisms. The modified hemp fiber improves the air permeability and mass transfer of the gel, increases the seed germination rate (germination rate is above 90%), germination potential and microbial survival rate, and can maintain seed vitality and bacterial activity for a long time. In addition, the modified hemp fiber plays a role in maintaining the mechanical strength of the gel ball structure, keeping the gel ball from being destroyed and the product structure stable.

[0030] (3) Sodium alginate gel provides carbon sources and other nutrients for the growth of microorganisms. Its pores also facilitate the transport of air, water and other substances into the gel, which is beneficial to the material exchange between seeds and bacterial flora, further enhancing their activity.

[0031] The present invention promotes the synergistic symbiotic effect of plants and microorganisms, and better realizes the plant-microorganism combined restoration effect on organic contaminated soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The scanning electron microscope pictures of jute fiber before (a) and after (b) alkali modification at 2000, 20000 and 50000 times magnification are shown;

[0033] Figure 2 The scanning electron microscope pictures of alkali-modified jute fiber loaded with petroleum hydrocarbon-degrading bacteria at 5000 times and 20000 times;

[0034] Figure 3 This is a photo of the seed gel ball product prepared in Example 1.

[0035] Figure 4 The results of measuring the number of petroleum hydrocarbon degrading bacteria in two seed gel balls after being stored at low temperature (4°C) for 35 days. Among them, (A) is the result of flow cytometry, (B) is the content of degrading bacteria in the gel ball; 1 is the hemp fiber seed gel ball prepared in Example 1, and 2 is the seed gel ball without hemp fiber. DETAILED DESCRIPTION

[0036] Example 1 Preparation of Seed Gel Balls for Soil Remediation

[0037] S1: Collect the newly harvested rapeseed seeds of the previous year, soak the rapeseed seeds in a 2% to 5% sodium hypochlorite solution for 15 minutes for sterilization, then rinse with clean water 3-5 times and dry them.

[0038] S2: Wash and drain the jute fiber in clean water, transfer to an oven and dry at 50-60°C, chop into 0.5-1mm pieces after drying, pass through a 60-100 mesh sieve, soak the sieved jute fiber in a 1mol / L sodium hydroxide solution with a solid-liquid mass volume ratio of 1g:5mL, soak for 12h, and then wash with distilled water until neutral, thereby obtaining alkali-modified jute fiber.

[0039] Scanning electron microscopy of jute fiber before and after modification Figure 1 As shown (before modification: a, after modification: b).

[0040] S3: After the petroleum hydrocarbon degrading bacteria (Acinetobacter junii) were cultured, the culture medium was removed by centrifugation, the cells were collected and resuspended in an equal volume of deionized water to obtain the petroleum hydrocarbon degrading bacteria solution, OD 600 is 1.7;

[0041] The alkali-modified hemp fiber was mixed with the petroleum hydrocarbon-degrading bacterial solution at a solid-liquid mass volume ratio of 1g:25mL, and placed in a constant temperature shaking incubator at 160-250r / min and 25°C for 3-8h. After centrifugation, the supernatant was discarded, washed, and dried to obtain the modified hemp fiber loaded with the degrading bacteria. The scanning electron microscopy image of the loaded degrading bacteria is shown in Figure 1. Figure 2 (5000 times and 20000 times).

[0042] S4: 25g / L sodium alginate solution with OD 600 The petroleum hydrocarbon degradation bacterial solution of 1.7 is mixed in a volume ratio of 9:1 to obtain sodium alginate-bacteria solution.

[0043] Sodium alginate-bacteria solution, modified hemp fiber loaded with degradation bacteria and rapeseed seeds are mixed evenly, and the ratio of modified hemp fiber loaded with degradation bacteria to sodium alginate-bacteria solution is 6g / L; crosslinking agent (35g / L calcium chloride solution) is slowly dripped into the mixed solution to obtain gel balls for soil repair, such as Figure 3 shown.

[0044] The sodium alginate-bacteria solution, the modified hemp fiber loaded with degrading bacteria and the rapeseed can be mixed evenly by magnetic stirring, and then the crosslinking agent solution is added thereto; the sodium alginate-bacteria solution can also be spread on the bottom of the culture dish, 1-5 mL each time, and the modified hemp fiber loaded with degrading bacteria and the rapeseed are added and mixed manually, and then the crosslinking agent solution is slowly added thereto, and the preparation is performed in multiple times.

[0045] Example 2 Contaminated soil remediation experiment

[0046] Specific methods for remediation of contaminated soil:

[0047] (1) Preparation of contaminated soil: The crude oil contaminated soil from Liaohe Oilfield was fully mixed with clean soil to prepare experimental contaminated soil with a total petroleum hydrocarbon concentration of 10-15 g / kg, which was sealed and stored for later use.

[0048] (2) Remediation steps: Add 400-500g of prepared petroleum hydrocarbon contaminated soil into the flower pot, and control the soil moisture content to 50%-60%. The three groups of experimental objects are: rapeseed naked seeds, seed gel balls prepared in Example 1, and rapeseed seed degradation bacteria gel balls without adding hemp fiber (the preparation method is that the hemp fiber loaded with microorganisms is not added, and the same degradation bacteria liquid as in Example 1 is mixed with sodium alginate solution and plant seeds, and calcium chloride solution is added for cross-linking). Each pot is treated with 10-15 seed composite degradation bacteria gel balls. Observe regularly every day, add water in an appropriate amount, and record the germination of rapeseed seeds. Collect the plants on the 60th day, collect soil samples, air-dry them, and seal them for storage. Determine the total petroleum hydrocarbon content in the soil and calculate the degradation rate of soil petroleum hydrocarbons. The measurement results are shown in Table 1.

[0049] Table 1 Rapeseed germination rate and soil petroleum hydrocarbon degradation rate in different treatment groups

[0050] Treatment Group Germination rate (10 days) Petroleum degradation rate in contaminated soil (60 days) Rapeseed naked seed 87.78％ 25.3％ Gel balls for soil repair prepared in Example 1 91.67％ 52.7％ Rapeseed degrading bacteria gel balls without adding hemp fiber 97.5％ 45.05％

[0051] Example 3 Mechanical Strength and Mass Transfer Determination of Gel Balls

[0052] Three groups of gel balls were set up, group 1: gel balls without adding seeds and hemp fibers, group 2: rapeseed seed degrading bacteria gel balls (hemp fibers without adding loaded bacteria), group 3: seed gel balls prepared in Example 1. The gel balls were randomly selected.

[0053] The preparation method of group 1 is: the same degrading bacterial solution in Example 1 is mixed with a sodium alginate solution, and a calcium chloride solution is added for cross-linking to obtain gel balls; the preparation method of group 2 is: the same degrading bacterial solution in Example 1 is mixed with a sodium alginate solution and plant seeds, and a calcium chloride solution is added for cross-linking to obtain seed gel balls.

[0054] The three groups of gel balls were placed in 150 mL conical flasks respectively, 60 mL of distilled water was added, and the flasks were shaken in a constant temperature shaking incubator for 48 h (160 rpm, 30°C). The damage of the gel balls was observed. The results are shown in Table 2 (the more "+" in mechanical strength, the greater the strength).

[0055] Three groups of experiments were set up. In each group, 0.5 mL of methylene blue solution and 20.0 mL of distilled water were added to a 50 mL conical flask, and then the three groups of gel balls were added, 20 in each group, and the mixture was shaken in a constant temperature shaking incubator for 24 h (160 rpm, 30°C). The absorbance value of the supernatant was measured at a wavelength of 406 nm. The mass transfer performance of the gel balls was measured by the absorbance difference before and after the reaction. The larger the absorbance difference, the better the mass transfer performance of the gel balls. The results are shown in Table 2.

[0056] Therefore, hemp fiber is beneficial to the mechanical strength of the gel ball and improves the mass transfer performance of the gel ball.

[0057] Table 2 Basic properties of gel balls with different formulations

[0058] Serial number deal with Particle size / mm Mechanical strength Mass transfer 1 Gel balls without rapeseed or hemp fiber added 3.554 + excellent 2 Rapeseed gel balls without added hemp fiber 4.223 ++ good 3 Added hemp fiber rapeseed gel balls 5.098 +++ excellent

[0059] Example 4

[0060] The seed gel balls prepared in Example 1 and the rapeseed seed degrading bacteria gel balls without adding hemp fiber (the preparation method is the same as Group 2 in Example 3) were taken, and after being stored at low temperature (4° C.) for 35 days, the number of petroleum hydrocarbon degrading bacteria in the two gel balls was determined.

[0061] The results are as follows Figure 4 As shown, (A) is the result of flow cytometry measurement, (B) is the content of degrading bacteria in the gel ball; 1 is the gel ball containing hemp fiber seeds prepared in Example 1, and 2 is the gel ball without hemp fiber seeds.

[0062] The results showed that the content of petroleum hydrocarbon degrading bacteria in the gel spheres prepared in Example 1 exceeded 1.6*10 9 cell / g. In the gel ball without adding hemp fiber, the content of petroleum hydrocarbon degrading bacteria is about 1.1*10 9 cell / g.

[0063] Seed gel balls with added hemp fiber had a greater microbial load and higher microbial survival rate after storage.

Claims

1. A seed gel ball for soil repair, characterized in that: The invention is composed of plant seeds and seed coating materials wrapped outside the plant seeds, wherein the seed coating materials are calcium alginate gel and modified hemp fibers doped in the calcium alginate gel; The modified hemp fiber and the calcium alginate gel are loaded with microorganisms; the modified hemp fiber is hemp fiber that has been subjected to acid modification or alkali modification, and the microorganisms are petroleum hydrocarbon degrading bacteria; The preparation method comprises the following steps: (1) The modified hemp fiber treated with acid or alkali is mixed with a microbial solution and cultured under shaking to obtain a modified hemp fiber loaded with microorganisms; (2) Mixing modified hemp fiber loaded with microorganisms, plant seeds, sodium alginate solution and microbial culture liquid; the modified hemp fiber content is 3-15 g / L, and the sodium alginate content is 10-35 g / L; (3) A cross-linking agent solution is added dropwise to the mixed solution obtained in step (2) to obtain seed gel balls for soil repair.

2. The seed gel ball according to claim 1, characterized in that: The oil-degrading bacteria are selected from Pseudomonas, Achromobacter, Arthrobacter, Micrococcus, Nocardia, Acinetobacter, Brevibacterium, Corynebacterium, Flavobacterium, and the fungi are Candida, Rhodotorula, Sporobacterium or Mycobacterium.

3. The seed gel ball according to claim 1, characterized in that: The plant seeds are rapeseed seeds.

4. The seed gel ball according to claim 1, characterized in that: The cross-linking agent is calcium chloride or calcium citrate, and the concentration of the cross-linking agent solution is 20-50 g / L.

5. Use of the seed gel ball according to any one of claims 1 to 4 in soil restoration.

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