Preparation method and application of composite soil conditioner capable of improving carbon sequestration effect

Abstract

The invention relates to the field of soil pollution treatment, and discloses a preparation method and application of a composite soil conditioner capable of improving the carbon sequestration effect, and the preparation method of the soil conditioner comprises the following steps: step A, preparing biochar; step B, preparing biochar microalgae particles; step C, preparation of oyster shell powder; d, coating particles to obtain an inner-layer soil conditioner and an outer-layer soil conditioner; the soil conditioner comprises an inner layer and an outer layer which are formed by adhesion of auxiliary materials, the inner layer comprises microalgae particles enriched and recycled by charcoal and can improve acid soil for a long time and provide organic matter and nitrogen and phosphorus nutrition, and the outer layer comprises roasted oyster shell powder and is rapid in soil acidity adjustment and capable of providing calcium salt. The composite soil conditioner has a synergistic effect of various materials, can be rapidly and slowly combined, can effectively improve acid soil, passivate soil heavy metals, provide organic matters, calcium, nitrogen, phosphorus and other nutritive salts for a relatively long time, improve the nutritional quality of vegetables and improve the carbon sequestration effect of soil, and has relatively good comprehensive benefits.

Description

Technical Field

[0001] The present invention relates to the field of soil pollution control, and more specifically, to a preparation method and application of a composite soil conditioner capable of improving carbon fixation effect. Background Art

[0002] Climate change has brought severe threats and challenges to human survival and development. The soil carbon pool is the largest carbon pool on land. Compared with industrial carbon sequestration, the synergistic effect of soil environmental pollution control and soil carbon sequestration is more cost-effective and is one of the important strategies for countries around the world to cope with climate change. It has attracted widespread attention at home and abroad. Therefore, in the new era of the "dual carbon" goal, it is an important demand for soil environmental governance technology to jointly utilize various solid waste resources with different carbon sequestration and soil conditioning characteristics, develop low-cost, high-efficiency, green and low-carbon soil conditioners, and synergize soil environmental pollution control with soil solid waste. Microalgae are widely distributed in the natural environment, with many species, large numbers, and fast growth. They can fix carbon through photosynthesis. At the same time, they can also absorb and accumulate heavy metals to prevent the absorption and accumulation of heavy metals in crops. The aquaculture tailwater contains a large amount of algae and fungi such as Microcystis aeruginosa, Nostoc commune, Chlorella minutissima, Scenedesmusobliquus, Chlamydomonsa Reinhardtii, and nitrogen and phosphorus nutrients, which have good recycling value. Waste wood mainly comes from construction sites, home decoration, waste furniture, wood processing plants and other fields. Its quantity has been increasing year by year with the development of the economy and the improvement of people's quality of life. Biochar has porosity and a large surface area. It decomposes slowly in the soil. It is not only a means of carbon fixation, but also a high-quality soil conditioner. Heat treatment of waste wood to make biochar is beneficial to soil conditioning and has a carbon fixation effect. The number of oyster shells in coastal areas of my country can reach millions of tons. They are generally directly piled up in the streets or dumped into the sea, polluting the environment. Oyster shell powder is rich in calcium carbonate and can quickly condition acidic soil. It can solidify heavy metals in the soil and provide calcium nutrition for crops, but excessive application will cause soil compaction.

[0003] In recent years, the technology of developing soil conditioners using microalgae, biochar, and oyster shell powder has developed rapidly. For example, patent number ZL202111085925.7, the invention name is "a microalgae ecological restoration agent for carbon fixation and prevention and control of arsenic pollution in paddy soil and its preparation method", freeze-dried microalgae cultured in phosphorus-free improved culture medium are applied to paddy soil to prevent arsenic pollution in paddy soil and play a role in carbon fixation, but the object of its treatment is only arsenic, the metal elements described are limited, and it needs to be cultured and transported under special environmental conditions, which has high efficiency and cost. Patent application number 202310981314.3, the invention name is "A soil fertilization conditioner and its preparation method", which is prepared by the synergistic effect of various materials such as alkali residue, calcium magnesium phosphate fertilizer, oyster shell, sepiolite, activator, rice husk, microbial agent, poultry and livestock manure, trace elements, paraffin oil, limonene, urea, etc. It can increase the pH and fertility of acidic soil, and improve the yield and quality of crops. However, its technology involves many materials, little utilization of solid waste resources, and does not consider the carbon fixation effect. Patent application number 202410154192.5, the invention name is "A soil conditioner based on organic acid activated oyster shell and its preparation method", with phosphate tailings powder and oxalic acid, roasted oyster shell powder and potassium alginate, unroasted oyster shell powder and other materials to form the inner, middle and outer layer structure materials, which can effectively improve acidic soil, passivate a variety of heavy metals, provide potassium fertilizer and phosphate fertilizer for the soil, and the fertilizer can be released slowly, but it does not consider the fast and slow effects of soil acidification and its carbon fixation effect. Patent application number 202211693095.0, the invention name is "A composite soil conditioner and its preparation method", which is made of biochar modified with sulfur-containing amino acids and oyster shell powder modified with organic acid metal complexes. Although it can passivate heavy metals in the soil for a long time, the required processing procedures are relatively complex and the processing cost is high. It does not consider the long-term performance of different materials to construct material hierarchies and their carbon fixation effects. Therefore, it is necessary to develop a more effective, simple, low-cost, and carbon-fixing soil conditioner preparation method. Recently, microalgae, biochar and oyster shell powder have different characteristics of carbon fixation and soil pollution remediation. There has been no report on their combined use to develop new green and low-carbon soil conditioners that can not only fix carbon, but also prevent and control heavy metal pollution and improve crop quality. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a microalgae biochar oyster shell powder composite soil conditioner that can improve the carbon fixation effect, recycle a variety of solid wastes at low cost, and combine the superior performance characteristics of different materials for hierarchical construction, develop and apply new green and low-carbon soil conditioners, so as to achieve the purpose of not only fixing carbon, but also preventing and controlling soil heavy metal pollution and improving crop quality.

[0005] To solve the above technical problems, the technical solution of the present invention is: A method for preparing a composite soil conditioner capable of improving carbon fixation effect comprises the following steps: Step A: biochar preparation; Step B: Preparation of biochar microalgae particles; Step C: Preparation of oyster shell powder; Step D: coating the particles to obtain inner and outer layers of soil conditioner.

[0006] Preferably: the soil conditioner comprises, by weight, 20-30 parts of waste wood biochar, 2-5 parts of microalgae, and 68-75 parts of oyster shell powder.

[0007] Preferably: the soil conditioner comprises an inner and outer layer bonded by auxiliary materials, the inner layer comprises microalgae particles enriched and recycled from aquaculture tail water using biochar, the outer layer is oyster shell powder gently stewed at 850°C, and the auxiliary material is a binder.

[0008] Preferably: in step A, the biochar is prepared by crushing the waste wood into 2 cm particles, adding the particles into a combustion furnace, passing nitrogen to maintain an oxygen-deficient state, pyrolyzing at 500° C. for 2 h, cooling to room temperature, and crushing through a 60-mesh sieve to obtain biochar particles.

[0009] Preferably: in step B, the biochar particles prepared in step A are added to aquaculture tail water, the microalgae and the nitrogen and phosphorus nutrients therein are recovered by precipitation enrichment, and the water is dried in a 40° C. oven to obtain biochar microalgae particles containing nitrogen and phosphorus nutrients.

[0010] Preferably: in step C, the oyster shell powder is prepared by washing the oyster shells, roasting them at a gentle temperature for 10 minutes, cooling them down, and crushing them through a 60-mesh sieve to obtain the oyster shell powder, and the roasting temperature is 850°C.

[0011] Preferably: in step D, the biochar microalgae particles prepared in step B are placed on a disc granulator, the surface of the biochar microalgae particles is sprayed with a binder, and the oyster shell powder is added to the rotating disc granulator so that the oyster shell powder is evenly coated on the surface of the biochar microalgae particles to obtain inner and outer layer soil conditioners.

[0012] Preferably: the binder is one or more of sodium carboxymethyl cellulose, calcium chloride, bentonite, and potassium alginate, the solution concentration is 2.5 mol / L, and the binder volume: oyster shell powder mass = 16:1.

[0013] Application of a composite soil conditioner that can enhance carbon fixation effect: The soil conditioner is applied in soil conditioning. The specific application method is: adding the obtained microalgae oyster biochar composite soil conditioner to the soil for soil conditioning, preventing and controlling the accumulation of heavy metals in crops, improving the nutritional quality of crops, and enhancing soil carbon fixation.

[0014] Preferably: according to the soil crop type and soil pollution status, 30-50kg of soil conditioner is added per mu. The outer layer of oyster shell powder quickly conditions the acidic soil, and the inner layer of microalgae biochar slowly improves the acidic soil and passivates various heavy metals in the soil. At the same time, it provides organic matter, calcium, nitrogen, phosphorus and other nutrients, improves the nutritional quality of vegetables, and enhances the soil carbon fixation effect.

[0015] The advantages and beneficial effects of the present invention are as follows: 1. This method uses biochar prepared by heat treatment of waste wood, coagulation and sedimentation to recycle and enrich microalgae in aquaculture tail water, and a variety of solid waste resources such as aquaculture solid waste oyster shells, and uses the properties of different materials to construct a soil conditioner in a hierarchical manner. It can combine fast and slow, first fast and then slowly condition acidic soil, passivate various heavy metals in the soil, and provide organic matter, calcium, nitrogen and phosphorus and other nutrients. Through the growth of algae and the effects of biochar, the carbon fixation effect of the soil and the nutritional quality of crops are improved.

[0016] 2. The composite soil conditioner of the present invention has been used to measure relevant experimental data on different vegetable soils and edible parts, confirming the beneficial effects of the microalgae biochar oyster shell powder composite soil conditioner, which can significantly increase the soil organic matter content, enhance the carbon fixation effect, prevent the absorption and accumulation of soil heavy metals in crops, and improve crop quality.

[0017] 3. The microalgae biochar and oyster shell powder composite soil conditioner selected by the present invention is prepared by combined and coordinated utilization of abundant solid waste resources, which is convenient for low-cost acquisition, storage and processing of production raw materials, can be mass-produced and promoted for use, and has high comprehensive benefits such as carbon fixation and environmental pollution control. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a SEM image of the biochar microalgae particles, oyster shell powder, and microalgae biochar oyster shell powder in the present invention; Figure 2 The XRD diagram of biochar, oyster shell powder, and microalgae biochar oyster shell powder in the present invention; Figure 3 It is the soil conditioning greenhouse simulation test data Appendix 1 of the present invention; Figure 4 This is the soil conditioning field application data Appendix 2 of the present invention. DETAILED DESCRIPTION

[0019] The subject matter described herein will now be discussed with reference to example embodiments. It should be understood that the discussion of these embodiments is only to enable those skilled in the art to better understand and implement the subject matter described herein, and the functions and arrangements of the elements discussed may be changed without departing from the scope of protection of the contents of this specification. Each example may omit, replace or add various processes or components as needed. In addition, the features described relative to some examples may also be combined in other examples.

[0020] Example 1 In this embodiment, a method for preparing a composite soil conditioner capable of improving carbon fixation effect is proposed, comprising the following steps: Step A: biochar preparation; The waste wood was crushed into 2 cm particles, added into the combustion furnace, and maintained in an oxygen-deficient state by nitrogen. It was pyrolyzed at 500 °C for 2 h, cooled to room temperature, and crushed through a 60-mesh sieve to obtain biochar particles.

[0021] Step B: Preparation of biochar microalgae particles; The biochar particles prepared in step A are added to aquaculture tail water, and the microalgae and the nitrogen and phosphorus nutrients therein are recovered by precipitation enrichment, and the water is dried in an oven at 40° C. to obtain biochar microalgae particles containing nitrogen and phosphorus nutrients.

[0022] Step C: Preparation of oyster shell powder; The oyster shells were cleaned, roasted at a gentle temperature for 10 minutes, cooled, and crushed through a 60-mesh sieve to obtain oyster shell powder. The roasting temperature was 850°C.

[0023] Step D: coating the particles to obtain inner and outer layers of soil conditioner.

[0024] The biochar microalgae particles prepared in step B are placed on a disc granulator, the surface of the biochar microalgae particles is sprayed with a binder, and the oyster shell powder is added to the rotating disc granulator so that the oyster shell powder is evenly coated on the surface of the biochar microalgae particles to obtain inner and outer layer soil conditioners.

[0025] The binder is sodium carboxymethyl cellulose, the solution concentration is 2.5 mol / L, and the binder volume: oyster shell powder mass = 16:1.

[0026] in: The soil conditioner comprises, by weight, 20 parts of waste wood biochar, 2 parts of microalgae, and 75 parts of oyster shell powder.

[0027] The soil conditioner includes an inner and outer layer bonded by auxiliary materials. The inner layer includes microalgae particles enriched with biochar and recycled aquaculture tail water. The outer layer is oyster shell powder gently stewed at 850°C. The auxiliary material is a binder.

[0028] Example 2 In this embodiment, a method for preparing a composite soil conditioner capable of improving carbon fixation effect is proposed, comprising the following steps: Step A: biochar preparation; The waste wood was crushed into 2 cm particles, added into the combustion furnace, and maintained in an oxygen-deficient state by nitrogen. It was pyrolyzed at 500 °C for 2 h, cooled to room temperature, and crushed through a 60-mesh sieve to obtain biochar particles.

[0029] Step B: Preparation of biochar microalgae particles; The biochar particles prepared in step A are added to aquaculture tail water, and the microalgae and the nitrogen and phosphorus nutrients therein are recovered by precipitation enrichment, and the water is dried in an oven at 40° C. to obtain biochar microalgae particles containing nitrogen and phosphorus nutrients.

[0030] Step C: Preparation of oyster shell powder; The oyster shells were cleaned, roasted at a gentle temperature for 10 minutes, cooled, and crushed through a 60-mesh sieve to obtain oyster shell powder. The roasting temperature was 850°C.

[0031] Step D: coating the particles to obtain inner and outer layers of soil conditioner.

[0032] The biochar microalgae particles prepared in step B are placed on a disc granulator, the surface of the biochar microalgae particles is sprayed with a binder, and the oyster shell powder is added to the rotating disc granulator so that the oyster shell powder is evenly coated on the surface of the biochar microalgae particles to obtain inner and outer layer soil conditioners.

[0033] The binder is calcium chloride and bentonite, the solution concentration is 2.5 mol / L, and the binder volume: oyster shell powder mass = 16:1.

[0034] in: The soil conditioner comprises, by weight, 25 parts of waste wood biochar, 3 parts of microalgae, and 71 parts of oyster shell powder.

[0035] The soil conditioner includes an inner and outer layer bonded by auxiliary materials. The inner layer includes microalgae particles enriched with biochar and recycled aquaculture tail water. The outer layer is oyster shell powder gently stewed at 850°C. The auxiliary material is a binder.

[0036] Example 3 In this embodiment, a method for preparing a composite soil conditioner capable of improving carbon fixation effect is proposed, comprising the following steps: Step A: biochar preparation; The waste wood was crushed into 2 cm particles, added into the combustion furnace, and maintained in an oxygen-deficient state by nitrogen. It was pyrolyzed at 500 °C for 2 h, cooled to room temperature, and crushed through a 60-mesh sieve to obtain biochar particles.

[0037] Step B: Preparation of biochar microalgae particles; The biochar particles prepared in step A are added to aquaculture tail water, and the microalgae and the nitrogen and phosphorus nutrients therein are recovered by precipitation enrichment, and the water is dried in an oven at 40° C. to obtain biochar microalgae particles containing nitrogen and phosphorus nutrients.

[0038] Step C: Preparation of oyster shell powder; The oyster shells were cleaned, roasted at a gentle temperature for 10 minutes, cooled, and crushed through a 60-mesh sieve to obtain oyster shell powder. The roasting temperature was 850°C.

[0039] Step D: coating the particles to obtain inner and outer layers of soil conditioner.

[0040] The biochar microalgae particles prepared in step B are placed on a disc granulator, the surface of the biochar microalgae particles is sprayed with a binder, and the oyster shell powder is added to the rotating disc granulator so that the oyster shell powder is evenly coated on the surface of the biochar microalgae particles to obtain inner and outer layer soil conditioners.

[0041] The binder is sodium carboxymethyl cellulose, calcium chloride, bentonite and potassium alginate, the solution concentration is 2.5 mol / L, and the volume of the binder: the mass of the oyster shell powder is 16:1.

[0042] in: The soil conditioner comprises, by weight, 30 parts of waste wood biochar, 5 parts of microalgae, and 68 parts of oyster shell powder.

[0043] The soil conditioner includes an inner and outer layer bonded by auxiliary materials. The inner layer includes microalgae particles enriched with biochar and recycled aquaculture tail water. The outer layer is oyster shell powder gently stewed at 850°C. The auxiliary material is a binder.

[0044] Example 4 In this embodiment, an application of a composite soil conditioner that can enhance carbon fixation effect is proposed.

[0045] The soil conditioner is applied in soil conditioning. The specific application method is: adding the obtained microalgae oyster biochar composite soil conditioner into the soil for soil conditioning, preventing and controlling the accumulation of heavy metals in crops, improving the nutritional quality of crops, and enhancing soil carbon fixation.

[0046] According to the soil crop type and soil pollution status, 30, 40 or 50 kg of soil conditioner is added per mu, preferably 40 kg in this embodiment. The outer layer of oyster shell powder quickly conditions the acidic soil, and the inner layer of microalgae biochar slowly improves the acidic soil, passivates various heavy metals in the soil, and provides organic matter, calcium, nitrogen, phosphorus and other nutrients, improves the nutritional quality of vegetables, and enhances the carbon fixation effect of the soil.

[0047] Example 5 In this embodiment, a microalgae oyster biochar composite soil conditioner capable of improving carbon fixation effect is prepared, which specifically includes the following steps: Step A: After the waste wood is crushed into 2 cm particles, it is added into the combustion furnace, nitrogen is passed to maintain an oxygen-deficient state, pyrolyzed at 500°C for 2 hours, cooled to room temperature, crushed through a 60-mesh sieve, and biochar particles are obtained.

[0048] Step B: Add 30 parts of biochar particles prepared in step A to the aquaculture tail water, precipitate and enrich and recover 2 parts of microalgae and their nitrogen and phosphorus nutrients, dry the water in a 40°C oven to obtain biochar microalgae particles containing nitrogen and phosphorus nutrients, as shown in the attached Figure 1 shown.

[0049] Step C: Wash the oyster shells, roast them at a gentle temperature for 10 minutes, then cool them down, and crush them through a 60-mesh sieve to obtain oyster shell powder. The roasting temperature is 850°C. Figure 1 shown.

[0050] Step D: Obtain inner and outer soil conditioners, place the biochar microalgae particles prepared in step B on a disc granulator, spray the surface of the biochar microalgae particles with potassium alginate binder, add 68 parts of oyster shell powder into the rotating disc granulator, the concentration of the potassium alginate binder solution is 2.5 mol / L, and the binder volume: oyster shell powder mass = 16:1, so that the oyster shell powder is evenly coated on the surface of the biochar microalgae particles to obtain inner and outer soil conditioners, as shown in the attached Figure 1 shown.

[0051] 60 kg of the obtained soil conditioner was evenly mixed with soil contaminated with cadmium (2.84 mg / kg) and arsenic (68 mg / kg), and placed in a natural light greenhouse at 25°C for potted cultivation. The crop planted was carrot (Daucus carotavar. sativa Hoffm). After 60 days of testing and sampling analysis, the results showed that the water extractable content in the soil was significantly reduced, the soil organic matter content was significantly increased, the cadmium and arsenic contents in the edible part of carrots were reduced by 61 µg / kg and 242 µg / kg, respectively, and the soluble sugar, soluble protein and vitamin C in the edible part of carrots were increased by 8 mg / g, 6 mg / g and 0.5 mg / g, respectively, which played a good role in carbon fixation, heavy metal pollution control and nutritional quality improvement. The results are shown in the attached figure. Figure 3 As shown in Schedule 1.

[0052] Example 6 In this embodiment, a microalgae oyster biochar composite soil conditioner capable of improving carbon fixation effect is prepared, which specifically includes the following steps: Step A: After the waste wood is crushed into 2 cm particles, it is added into the combustion furnace, nitrogen is passed to maintain an oxygen-deficient state, and pyrolysis is carried out at 500 ° C for 2 h. After cooling to room temperature, the waste wood is crushed and passed through a 60-mesh sieve to obtain biochar particles. The XRD characterization is shown in the attached figure. Figure 2 shown.

[0053] Step B: Add 28 parts of biochar particles prepared in step A into aquaculture tail water, precipitate and enrich and recover 3 parts of microalgae and their nitrogen and phosphorus nutrients therein, dry the water in a 40°C oven, and obtain biochar microalgae particles containing nitrogen and phosphorus nutrients.

[0054] Step C: Wash the oyster shells, calcine them at a gentle temperature for 10 minutes, cool them down, and crush them through a 60-mesh sieve to obtain oyster shell powder. The calcination temperature is 850°C. The XRD characteristics are as shown in the attached figure. Figure 2 shown.

[0055] Step D: Obtain inner and outer soil conditioners. Place the biochar microalgae particles prepared in step B on a disc granulator, spray the surface of the biochar microalgae particles with potassium alginate binder, add 69 parts of oyster shell powder into the rotating disc granulator, and add the sodium carboxymethyl cellulose binder solution with a concentration of 2.5 mol / L, and the binder volume: oyster shell powder mass = 16:1, so that the oyster shell powder is evenly coated on the surface of the biochar microalgae particles to obtain inner and outer soil conditioners. The XRD characterization is shown in the attached figure. Figure 2 shown.

[0056] 60 kg of the obtained microalgae biochar oyster shell powder composite soil conditioner was evenly mixed with cadmium (2.84 mg / kg) and arsenic (68 mg / kg) contaminated soil, and placed in a 25°C, natural light greenhouse for potted cultivation. The crop planted was carrot (Daucuscarota var. sativa Hoffm). After 60 days of testing and analysis, the results showed that the water extractable content in the soil was significantly reduced, the soil organic matter content was significantly increased, the cadmium and arsenic contents in the edible part of carrots were reduced by 63 µg / kg and 245 µg / kg, respectively, and the soluble sugar, soluble protein and vitamin C in the edible part of carrots were increased by 7 mg / g, 5 mg / g and 0.6 mg / g, respectively, which played a good role in carbon fixation, heavy metal pollution control and nutritional quality improvement. The results are shown in the attached figure. Figure 3 As shown in Schedule 1.

[0057] Example 7 In this embodiment, a microalgae oyster biochar composite soil conditioner capable of improving carbon fixation effect is prepared, which specifically includes the following steps: Step A: After the waste wood is crushed into 2 cm particles, it is added into the combustion furnace, nitrogen is passed to maintain an oxygen-deficient state, pyrolyzed at 500°C for 2 hours, cooled to room temperature, crushed through a 60-mesh sieve, and biochar particles are obtained.

[0058] Step B: Add 26 parts of biochar particles prepared in step A to aquaculture tail water, precipitate and enrich and recover 3 parts of microalgae and their nitrogen and phosphorus nutrients, dry the water in a 40°C oven, and obtain biochar microalgae particles containing nitrogen and phosphorus nutrients.

[0059] Step C: Wash the oyster shells, roast them at a gentle temperature for 10 minutes, then cool them down, and crush them through a 60-mesh sieve to obtain oyster shell powder, wherein the roasting temperature is 850°C.

[0060] Step D: obtaining inner and outer layer soil conditioners, placing the biochar microalgae particles prepared in step B on a disc granulator, spraying the surface of the biochar microalgae particles with a calcium chloride binder, adding 71 parts of oyster shell powder into the rotating disc granulator, the concentration of the potassium alginate binder solution is 2.5 mol / L, and the binder volume: oyster shell powder mass = 16:1, so that the oyster shell powder is evenly coated on the surface of the biochar microalgae particles to obtain inner and outer layer soil conditioners.

[0061] 60 kg of the obtained microalgae biochar oyster shell powder composite soil conditioner was evenly mixed with cadmium (2.84 mg / kg) and arsenic (68 mg / kg) contaminated soil, and placed in a 25°C, natural light greenhouse for potted cultivation. The crop planted was green pepper (Capsicumannuum var. grossum). After 60 days of testing and analysis, the results showed that the water extractable content in the soil was significantly reduced, the soil organic matter content was significantly increased, the cadmium and arsenic contents in the edible part of the green pepper were reduced by 69 µg / kg and 235 µg / kg, respectively, and the soluble sugar, soluble protein and vitamin C in the edible part of the green pepper were increased by 8 mg / g, 10 mg / g and 2.0 mg / g, respectively, which played a good role in carbon fixation, heavy metal pollution control and nutritional quality improvement. The results are shown in the attached figure. Figure 3 As shown in Schedule 1.

[0062] Comparative Example 1 In this comparative example, a microalgae oyster biochar composite soil conditioner capable of improving carbon fixation effect is prepared, which specifically comprises the following steps: Step A: After the waste wood is crushed into 2 cm particles, it is added into the combustion furnace, nitrogen is passed to maintain an oxygen-deficient state, pyrolyzed at 500°C for 2 hours, cooled to room temperature, crushed through a 60-mesh sieve, and biochar particles are obtained.

[0063] Step B, adding 24 parts of biochar particles prepared in step A to aquaculture tail water, precipitating and enriching and recovering 4 parts of microalgae and nitrogen and phosphorus nutrients therein, drying the water in a 40° C. oven to obtain biochar microalgae particles containing nitrogen and phosphorus nutrients.

[0064] Step C, washing the oyster shells, roasting them at a gentle temperature for 10 minutes, cooling them, and crushing them through a 60-mesh sieve to obtain oyster shell powder, wherein the roasting temperature is 850°C.

[0065] Step D, obtaining inner and outer layer soil conditioners, placing the biochar microalgae particles prepared in step B on a disc granulator, spraying the surface of the biochar microalgae particles with a bentonite binder, adding 72 parts of oyster shell powder to the rotating disc granulator, the concentration of the potassium alginate binder solution is 2.5 mol / L, and the binder volume: oyster shell powder mass = 16:1, so that the oyster shell powder is evenly coated on the surface of the biochar microalgae particles to obtain inner and outer layer soil conditioners.

[0066] 60 kg of the obtained microalgae biochar oyster shell powder composite soil conditioner was evenly mixed with cadmium (2.84 mg / kg) and arsenic (68 mg / kg) contaminated soil, and placed in a 25°C, natural light greenhouse for potted cultivation. The crop planted was carrot (Daucuscarota var. sativa Hoffm). After 60 days of testing and analysis, the results showed that the water extractable content in the soil was significantly reduced, the soil organic matter content was significantly increased, the cadmium and arsenic contents in the edible part of carrots were reduced by 67 µg / kg and 231 µg / kg, respectively, and the soluble sugar, soluble protein and vitamin C in the edible part of carrots were increased by 10 mg / g, 8 mg / g and 0.7 mg / g, respectively, which played a good role in carbon fixation, heavy metal pollution control and nutritional quality improvement. The results are shown in the attached figure. Figure 3 As shown in Schedule 1.

[0067] Comparative Example 2 In this comparative example, a microalgae oyster biochar composite soil conditioner capable of improving carbon fixation effect is prepared, which specifically comprises the following steps: Step A: After the waste wood is crushed into 2 cm particles, it is added into the combustion furnace, nitrogen is passed to maintain an oxygen-deficient state, pyrolyzed at 500°C for 2 hours, cooled to room temperature, crushed through a 60-mesh sieve, and biochar particles are obtained.

[0068] Step B, adding 23 parts of biochar particles prepared in step A to aquaculture tail water, precipitating and enriching and recovering 3 parts of microalgae and their nitrogen and phosphorus nutrients therein, drying the water in a 40° C. oven to obtain biochar microalgae particles containing nitrogen and phosphorus nutrients.

[0069] Step C, washing the oyster shells, roasting them at a gentle temperature for 10 minutes, cooling them, and crushing them through a 60-mesh sieve to obtain oyster shell powder, wherein the roasting temperature is 850°C.

[0070] Step D, obtaining inner and outer layer soil conditioners, placing the biochar microalgae particles prepared in step B on a disc granulator, spraying the surface of the biochar microalgae particles with a potassium alginate binder, adding 74 parts of oyster shell powder to the rotating disc granulator, the concentration of the potassium alginate binder solution is 2.5 mol / L, and the binder volume: oyster shell powder mass = 16:1, so that the oyster shell powder is evenly coated on the surface of the biochar microalgae particles to obtain inner and outer layer soil conditioners.

[0071] 60 kg of the obtained microalgae biochar oyster shell powder composite soil conditioner was evenly mixed with cadmium (2.84 mg / kg) and arsenic (68 mg / kg) contaminated soil, and placed in a 25°C, natural light greenhouse for potted cultivation. The crop planted was green pepper (Capsicumannuum var. grossum). After 60 days of testing and analysis, the results showed that the water extractable content in the soil was significantly reduced, the soil organic matter content was significantly increased, the cadmium and arsenic contents in the edible part of the green pepper were reduced by 72 µg / kg and 232 µg / kg, respectively, and the soluble sugar, soluble protein and vitamin C in the edible part of the green pepper were increased by 6 mg / g, 8 mg / g and 1.6 mg / g, respectively, which played a good role in carbon fixation, heavy metal pollution control and nutritional quality improvement. The results are shown in the attached figure. Figure 3 As shown in Schedule 1.

[0072] Application Case 1 The conditioned soil to be polluted was selected from a carrot field in the coastal area of ​​Fujian Province. The main heavy metal pollutants in the soil were lead and cadmium. The composite soil conditioner of Implementation Case 6 was selected, and the application experimental group was divided into a control group (no soil conditioner was applied) and experimental group 1 (Implementation Case 6). The experimental area of ​​each group was 0.5 mu, and the planting density was 12,000 plants / mu. Before applying the soil conditioner, the application experimental group was sampled, and samples from 8-10 points were collected in the two groups according to the diagonal method. After mixing evenly, the control group soil sample was obtained by the quartering method. After soil sampling, 80 kg of soil conditioner was evenly applied in the test area according to the experimental design. Four months after routine field management, soil samples and the edible parts of green peppers were collected again using the same method mentioned above. The results are shown in the attached figure. Figure 4 As shown in the attached Table 2, the results show that the application of the composite soil conditioner of the present invention can improve acidified soil, increase soil organic matter, prevent the absorption and accumulation of soil polluted heavy metals in crops, and improve the nutritional quality of crops.

[0073] Application Case 2 The conditioned soil to be polluted was selected from a green pepper field in the coastal area of ​​Fujian Province. The main heavy metal pollutants in the soil were lead and cadmium. The composite soil conditioner of Implementation Case 7 was selected, and the application experimental group was divided into a control group (no soil conditioner was applied) and experimental group 2 (Implementation Case 7). The experimental area of ​​each group was 0.5 mu, and the planting density was 9,000 plants / mu. Before applying the soil conditioner, the application experimental group was sampled, and samples from 8-10 points were collected in the two groups according to the diagonal method. After mixing evenly, the control group soil sample was obtained by the quartering method. After soil sampling, 80 kg of soil conditioner was evenly applied in the test area according to the experimental design. Four months after routine field management, soil samples and the edible parts of green peppers were collected again using the same method mentioned above. The results are shown in the attached figure. Figure 4 As shown in the attached Table 2, the results show that the application of the composite soil conditioner of the present invention can improve acidified soil, increase soil organic matter, prevent the absorption and accumulation of soil polluting heavy metals in crops, and improve the nutritional quality of crops.

[0074] The above describes an embodiment of the present embodiment, but the present embodiment is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present embodiment, ordinary technicians in this field can also make many forms, all of which are within the protection of the present embodiment.

Claims

1. A method for preparing a composite soil conditioner capable of improving carbon fixation effect, characterized in that: The following steps are involved: Step A: biochar preparation; Step B: Preparation of biochar microalgae particles; Step C: preparation of oyster shell powder; Step D: coating the particles to obtain inner and outer layers of soil conditioner.

2. The method for preparing a composite soil conditioner capable of improving carbon fixation effect according to claim 1, characterized in that: The soil conditioner comprises, by weight, 20-30 parts of waste wood biochar, 2-5 parts of microalgae, and 68-75 parts of oyster shell powder.

3. The method for preparing a composite soil conditioner capable of improving carbon fixation effect according to claim 2, characterized in that: The soil conditioner comprises an inner and outer layer bonded by auxiliary materials, wherein the inner layer comprises microalgae particles obtained by enriching and recycling aquaculture tail water using biochar, and the outer layer is oyster shell powder gently stewed at 850°C, and the auxiliary material is a binder.

4. The method for preparing a composite soil conditioner capable of improving carbon fixation effect according to claim 1, characterized in that: In step A, the biochar is prepared by crushing the waste wood into 2 cm particles, adding the particles into a combustion furnace, passing nitrogen to maintain an oxygen-deficient state, pyrolyzing at 500° C. for 2 h, cooling to room temperature, crushing the particles through a 60-mesh sieve, and obtaining biochar particles.

5. The method for preparing a composite soil conditioner capable of improving carbon fixation effect according to claim 1, characterized in that: In step B, the biochar particles prepared in step A are added to aquaculture tail water, the microalgae and the nitrogen and phosphorus nutrients therein are recovered by precipitation enrichment, and the water is dried in an oven at 40° C. to obtain biochar microalgae particles containing nitrogen and phosphorus nutrients.

6. The method for preparing a composite soil conditioner capable of improving carbon fixation effect according to claim 1, characterized in that: In step C, the oyster shell powder is prepared by washing the oyster shells, roasting them at a gentle temperature for 10 minutes, cooling them, and crushing them through a 60-mesh sieve to obtain the oyster shell powder. The roasting temperature is 850°C.

7. The method for preparing a composite soil conditioner capable of improving carbon fixation effect according to claim 1, characterized in that: In step D, the biochar microalgae particles prepared in step B are placed on a disc granulator, the surface of the biochar microalgae particles is sprayed with a binder, and oyster shell powder is added to the rotating disc granulator so that the oyster shell powder is evenly coated on the surface of the biochar microalgae particles to obtain inner and outer layer soil conditioners.

8. The method for preparing a composite soil conditioner capable of improving carbon fixation effect according to claim 3, characterized in that: The binder is one or more of sodium carboxymethyl cellulose, calcium chloride, bentonite, and potassium alginate, the solution concentration is 2.5 mol / L, and the binder volume: oyster shell powder mass = 16:

1.

9. An application of a composite soil conditioner capable of improving carbon fixation effect, characterized in that: The soil conditioner is applied in soil conditioning. The specific application method is: adding the obtained microalgae oyster biochar composite soil conditioner into the soil for soil conditioning, preventing and controlling the accumulation of heavy metals in crops, improving the nutritional quality of crops, and enhancing soil carbon fixation.

10. The use of a composite soil conditioner capable of improving carbon fixation effect according to claim 9, characterized in that: Add 30-50kg soil conditioner per mu according to soil crop type and soil pollution status.

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