Remediation method for garden polluted soil

Abstract

The invention discloses a remediation method for garden contaminated soil, and belongs to the technical field of garden soil remediation, the method comprises the following steps: regulating the pH value of soil to activate heavy metal contaminated soil, then applying a remediation agent to fix heavy metal ions in the soil, and then sowing hyperaccumulator inoculated with arbuscular mycorrhizal fungi. Heavy metal ions in the soil are fixed by applying a repairing agent, so that the hyperaccumulator can well germinate and grow without being stressed by the heavy metal ions, and further more heavy metal ions in the soil can be absorbed and enriched; on one hand, the inoculated arbuscular mycorrhizal fungi can secrete organic acid to activate and release the heavy metal ions fixed by the repairing agent, so that the heavy metal ions are gradually absorbed and enriched by the plants, and on the other hand, the absorption efficiency of the plants on the heavy metal ions can be improved; the hyperaccumulator can well grow in the heavy metal contaminated soil, so that heavy metal ions in the soil are effectively absorbed and removed, and the heavy metal contaminated garden soil is efficiently repaired.

Description

Technical Field

[0001] The invention relates to the technical field of garden soil restoration, and in particular to a method for restoring garden polluted soil. Background Art

[0002] Gardens are beautiful natural environments and recreational areas created by using engineering technology and artistic means in a certain area, by transforming the terrain, or further building mountains, stacking stones, managing water, planting trees and flowers, creating buildings, and arranging garden paths. With the development of the country, the improvement of urbanization, and the promotion of the concept of green life, urban garden landscapes are becoming more and more common. At present, gardens are mainly based on planting vegetation, and soil is the basis for the growth of these garden vegetation.

[0003] Due to the pollution of factory emissions, excessive use of fertilizers and pesticides, unreasonable irrigation, etc., the soil structure and physical and chemical properties are destroyed, resulting in excessive heavy metals in the soil, poor air permeability, reduced water retention capacity and other problems. The existence of these problems seriously affects the survival rate and growth of garden greening plants, among which the excessive heavy metal ions in the soil have a significant impact. At present, the method of guest soil and the method of applying repair agents are generally used to repair garden soil, but the construction volume of the guest soil method is large, the investment cost is high, the soil structure is destroyed, and there is a problem of dirty soil treatment; the application of repair agents is simple to operate, but the repair agents currently on the market have a single effect, and excessive application of repair agents will damage the soil, and the use of repair agents cannot completely remove heavy metal ions in the soil, which is easy to cause secondary pollution; the plant repair method is a method of completely removing heavy metal ions in the soil by planting plants to absorb and enrich heavy metal ions in the soil. It has advantages in economy, ecology, and environmental protection, but when planting plants under conventional methods, it is easy to be affected by heavy metal stress, which affects plant growth and reduces biomass, resulting in poor plant repair effects and long repair time.

[0004] Therefore, there is a need to find a method for repairing garden contaminated soil to solve the problem that when planting plants to repair heavy metal contaminated garden soil under conventional methods, plants are easily affected by heavy metal stress, which affects plant growth, resulting in poor plant repair effect and long repair time. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for repairing garden contaminated soil, so as to solve the problem that when planting plants to repair heavy metal contaminated garden soil under conventional methods, plants are easily affected by heavy metal stress, which affects plant growth, resulting in poor plant repair effect and long repair time.

[0006] The present invention solves the above technical problems by the following technical means:

[0007] A method for repairing garden contaminated soil, the method comprising the following steps:

[0008] (1) After removing weeds and impurities from the soil, plow the soil, adjust the soil pH to 4.5-5.5, and leave it to stand for 5-10 days;

[0009] (2) At 9-10 am on a sunny day, apply 0.1-0.3 kg / m 2 Spray the repair agent on the soil in the amount of 1000 mg / kg, and plough the soil to a depth of 20-30 cm 4 hours after spraying. After ploughing, spray the repair agent for the second time with the same amount. Adjust the soil pH to 6-7 3-6 days after applying the repair agent.

[0010] (3) adding the super-enriched plant seeds after germination to the substrate inoculated with arbuscular mycorrhizal fungi, mixing evenly and then sowing;

[0011] (4) After the hyperaccumulator plants are mature, they are uprooted and then the hyperaccumulator plants are repeatedly planted according to the method in step (3) until the heavy metal ion content in the soil meets the standard of "Soil Environmental Quality Agricultural Land Soil Risk Control Standard (Trial)" (GB15618-2018), and the restored garden soil is obtained, and garden plants can be planted according to conventional methods.

[0012] The present invention selects vetiver / centipede grass, a plant with good absorption and enrichment effects on various heavy metal ions, for sowing, so that it absorbs and enriches heavy metal ions in the soil during its growth process, and then uproots the mature vetiver / centipede grass that has absorbed and enriched the heavy metal ions, thereby completely removing the heavy metal ions in the soil and performing green and efficient repair of heavy metal-contaminated garden soil.

[0013] Furthermore, the repair agent in step (2) includes the following raw materials:

[0014] Chitosan, 50wt% isopropanol aqueous solution, 1,2-butylene oxide, nano silicon dioxide, L-asparagine and dithiothreitol.

[0015] Further, the preparation method of the repair agent is as follows:

[0016] A: Add chitosan to 50wt% isopropanol aqueous solution and stir to disperse, let stand for 2-6h, then add 1,2-butylene oxide, stir at room temperature for 1h, then heat to 60-70℃ and continue to react for 20-40min, filter to remove the filtrate after the reaction is completed, and then dry at 45℃ to obtain modified chitosan;

[0017] B: Add nano-silica into water and stir to disperse, heat to 60-80°C and keep warm for 1-2 hours, then add dithiothreitol and react at constant temperature for 30-60 minutes, then cool to 40-50°C and add L-asparagine to react for 1-2 hours, after the reaction is completed, filter to remove the filtrate and place at 4°C for cold treatment overnight to obtain pre-treated nano-silica;

[0018] C: Add water to the modified chitosan to prepare a 2wt% modified chitosan solution, immediately add the pretreated nano-silicon dioxide, mix well, and then stand at 4°C for 12-24 hours to obtain a repair agent.

[0019] The present invention repairs heavy metal contaminated soil by planting hyperaccumulators. However, under the stress of heavy metal ions, the germination and growth of the hyperaccumulators will be significantly inhibited, reducing the repair effect. Therefore, the present invention prepares a repair agent to treat the soil to adsorb and fix the heavy metal ions in the soil, thereby eliminating the stress of the heavy metal ions on the hyperaccumulators, ensuring the good germination and growth of the hyperaccumulators. At the same time, arbuscular mycorrhizal fungi are inoculated when the hyperaccumulators are sown. The physiological metabolic activities of the arbuscular mycorrhizal fungi release organic acids to gradually activate the heavy metal ions adsorbed and fixed by the repair agent, so that the heavy metal ions are gradually released and absorbed and enriched by the plants, and the absorption and enrichment of the heavy metal ions by the plants is increased. Through the combined action of the repair agent, the hyperaccumulators and the arbuscular mycorrhizal fungi, the good growth of the hyperaccumulators and the efficient absorption and enrichment of the heavy metal ions are ensured, thereby realizing rapid and efficient repair of the heavy metal contaminated soil.

[0020] Furthermore, in step A, the mass ratio of chitosan, 50 wt% isopropanol aqueous solution, and 1,2-butylene oxide is (0.5-1): (5-10): (0.2-0.5).

[0021] Furthermore, in step B, the mass ratio of nano-silica, dithiothreitol, and L-asparagine is (2-4): (0.2-0.5): (0.1-0.2).

[0022] Furthermore, in step C, the mass ratio of the 2 wt % modified chitosan solution to the pretreated nano-silicon dioxide is (5-10): (2-4).

[0023] Furthermore, the super-accumulator plant in the step is any one of Vetiveria zizanioides and Scolopendra subspinipes.

[0024] Furthermore, the super-enriched plant seed germination operation in step (3) is specifically as follows:

[0025] The super-enriched plant seeds are soaked in 75% ethanol solution for 30 seconds, then placed in 0.1% mercuric chloride solution for disinfection for 5-8 minutes, and then washed with sterile water for 5 times to obtain disinfected seeds; the disinfected seeds are soaked in clean water for 12-24 hours to obtain pre-treated seeds; the pre-treated seeds are placed in a culture dish covered with 2 layers of filter paper, the filter paper is soaked with water and then placed in an incubator, and germinated at 25°C in dark conditions until the seeds turn white to obtain the super-enriched plant seeds after germination.

[0026] Furthermore, the specific operation of inoculating the substrate with arbuscular mycorrhizal fungi in step (3) is as follows:

[0027] Peat soil and coconut bran were mixed at a volume ratio of 1:2 to obtain a matrix, and arbuscular mycorrhizal fungi were mixed at a mass ratio of matrix:arbuscular mycorrhizal fungi=50:1 to obtain a matrix inoculated with arbuscular mycorrhizal fungi.

[0028] Furthermore, the arbuscular mycorrhizal fungus is Glomus mosseae.

[0029] Beneficial effects:

[0030] 1. The present invention absorbs and enriches heavy metal ions in garden soil by planting plants that have good absorption and enrichment effects on various heavy metal ions, and then uproots the plants that have absorbed and enriched heavy metal ions, thereby completely removing excess heavy metal ions in the soil, improving soil properties, and achieving green and efficient remediation of heavy metal-contaminated garden soil.

[0031] 2. Before planting hyperaccumulator plants, the present invention first activates the heavy metal contaminated soil, then applies a repair agent to repair and fix the heavy metal ions in the soil, thereby eliminating the stress of heavy metal ions on plant germination and growth, promoting better growth of plants to repair the soil; and inoculating arbuscular mycorrhizal fungi when planting plants. The arbuscular mycorrhizal fungi secrete organic acids to gradually release the heavy metal ions fixed by the repair agent to be absorbed and enriched by the plants, while increasing the absorption and enrichment of heavy metal ions by the plants. The combined effect of each step effectively improves the repair effect of heavy metal contaminated garden soil. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to specific embodiments:

[0033] Example 1: Preparation of repair agent

[0034] A: 0.6 kg of chitosan was added to 6 kg of 50 wt% isopropanol aqueous solution and stirred and dispersed. After standing for 4 hours, 0.3 kg of 1,2-butylene oxide was added. After stirring at room temperature for 1 hour, the temperature was raised to 65°C and the reaction was continued for 30 minutes. After the reaction was completed, the filtrate was filtered out and then dried at 45°C to obtain modified chitosan;

[0035] B: 3 kg of nano-silica was added to 15 kg of water and stirred for dispersion, the temperature was raised to 70°C and kept warm for 1.5 hours, then 0.3 kg of dithiothreitol was added and reacted at a constant temperature for 40 minutes, then the temperature was lowered to 45°C and 0.15 kg of L-asparagine was added and reacted for 1.5 hours, after the reaction was completed, the filtrate was filtered out and placed at 4°C for cold treatment overnight to obtain pre-treated nano-silica;

[0036] C: Add water to the modified chitosan to prepare 7 kg of 2 wt% modified chitosan solution, immediately add 3 kg of pretreated nano-silicon dioxide, mix well, and let stand at 4°C for 18 hours to obtain a repair agent.

[0037] Example 2: Preparation of repair agent 2

[0038] A: 0.5 kg of chitosan was added to 5 kg of 50 wt% isopropanol aqueous solution and stirred and dispersed. After standing for 2 hours, 0.2 kg of 1,2-butylene oxide was added. After stirring at room temperature for 1 hour, the temperature was raised to 60°C and the reaction was continued for 20 minutes. After the reaction was completed, the filtrate was filtered out and then dried at 45°C to obtain modified chitosan;

[0039] B: Add 2kg of nano-silica to 10kg of water and stir to disperse, heat to 60°C and keep warm for 1h, then add 0.2kg of dithiothreitol and react at constant temperature for 30min, then cool to 40°C and add 0.1kg of L-asparagine to react for 1h, after the reaction is completed, filter to remove the filtrate and place at 4°C for cold treatment overnight to obtain pretreated nano-silica;

[0040] C: Add water to the modified chitosan to prepare 5 kg of 2 wt% modified chitosan solution, immediately add 2 kg of pretreated nano-silicon dioxide, mix well, and let stand at 4°C for 16 hours to obtain a repair agent.

[0041] Example 3: Preparation of repair agent 3

[0042] A: 1 kg of chitosan was added to 10 kg of 50 wt% isopropanol aqueous solution and stirred and dispersed. After standing for 6 hours, 0.5 kg of 1,2-butylene oxide was added. After stirring at room temperature for 1 hour, the temperature was raised to 70°C and the reaction was continued for 40 minutes. After the reaction was completed, the filtrate was filtered out and then dried at 45°C to obtain modified chitosan;

[0043] B: 4 kg of nano-silica was added to 20 kg of water and stirred for dispersion, the temperature was raised to 80°C and kept warm for 1 hour, then 0.5 kg of dithiothreitol was added and reacted at a constant temperature for 60 minutes, then the temperature was lowered to 40°C and 0.2 kg of L-asparagine was added and reacted for 2 hours, after the reaction was completed, the filtrate was filtered out and placed at 4°C for cold treatment overnight to obtain pre-treated nano-silica;

[0044] C: Add water to the modified chitosan to prepare 10 kg of 2 wt% modified chitosan solution, immediately add 4 kg of pretreated nano-silicon dioxide, mix well, and let stand at 4°C for 24 hours to obtain a repair agent.

[0045] Comparative Example 1: Preparation of repair agent

[0046] In contrast to Example 1, the only difference is that in the preparation of the repair agent in Comparative Example 1, chitosan is not modified in step A, that is, chitosan is directly used in step C to prepare the chitosan solution.

[0047] Comparative Example 2: Preparation of repair agent

[0048] In contrast to Example 1, the only difference is that dithiothreitol is not added in step B when preparing the repair agent in Comparative Example 2, as follows:

[0049] A: Same as Example 1;

[0050] B: Add 3kg of nano-silica to 15kg of water and stir to disperse, heat to 70°C and keep warm for 1.5h, then cool to 45°C and add 0.15kg of L-asparagine to react for 1.5h. After the reaction is completed, filter to remove the filtrate and place at 4°C for cold treatment overnight to obtain pretreated nano-silica;

[0051] C: Same as Example 1.

[0052] Comparative Example 3: Preparation of repair agent

[0053] In contrast to Example 1, the only difference is that L-asparagine is not added in step B when preparing the repair agent in Comparative Example 3, as follows:

[0054] A: Same as Example 1;

[0055] B: Add 3kg of nano-silicon dioxide into 15kg of water and stir to disperse, heat to 70°C and keep warm for 1.5h, then add 0.3kg of dithiothreitol and keep warm for 40min. After the reaction is completed, filter and remove the filtrate and place it at 4°C for cold treatment overnight to obtain pretreated nano-silicon dioxide;

[0056] C: Same as Example 1.

[0057] Comparative Example 4: Preparation of repair agent

[0058] In contrast to Example 1, the only difference is that in Comparative Example 4, the preparation of the repairing agent lacks step B, and the nano-silicon dioxide is not pretreated, but conventional nano-silicon dioxide is used, as follows:

[0059] A: Same as Example 1;

[0060] B: Add water to the modified chitosan to prepare 7 kg of 2 wt% modified chitosan solution, immediately add 3 kg of nano-silicon dioxide and mix well, then let stand at 4°C for 18 hours to obtain the repair agent.

[0061] Comparative Example 5: Preparation of repair agent

[0062] In contrast to Example 1, the only difference is that in the preparation of the repair agent in Comparative Example 5, no cold treatment is performed in step B, as follows:

[0063] A: Same as Example 1;

[0064] B: 3 kg of nano-silicon dioxide was added to 15 kg of water and stirred for dispersion, the temperature was raised to 70°C and kept warm for 1.5 hours, then 0.3 kg of dithiothreitol was added and reacted at a constant temperature for 40 minutes, then the temperature was lowered to 45°C and 0.15 kg of L-asparagine was added and reacted for 1.5 hours, after the reaction was completed, the filtrate was removed by filtration to obtain the pretreated nano-silicon dioxide;

[0065] Comparative Example 6: Preparation of repair agent

[0066] In contrast to Example 1, the only difference is that the repair agent in Comparative Example 6 lacks steps A and B when preparing the repair agent, that is, conventional chitosan and conventional nano-silicon dioxide are directly used to prepare the repair agent, as follows:

[0067] Water was added to chitosan to prepare 7 kg of 2 wt% chitosan solution, and 3 kg of nano-silicon dioxide was immediately added and mixed evenly, and then allowed to stand at 4° C. for 18 hours to obtain a repair agent.

[0068] Example 4: Garden soil remediation

[0069] (1) After removing weeds and impurities from the soil, the soil was tilled to a depth of about 35 cm. After tilling, the soil pH was adjusted to 5 and the soil was left to stand for 8 days;

[0070] (2) At 9:00 a.m. on a sunny day, 0.2 kg / m 2 The repair agent prepared in Example 3 was sprayed on the soil in an amount of , and the soil was tilled to a depth of about 25 cm 4 hours after spraying. After tilling, the repair agent was sprayed a second time in the same amount. The soil pH was adjusted to 6.5 4 days after the repair agent was applied;

[0071] (3) Vetiver seeds were soaked in 75% ethanol solution for 30 seconds, then placed in 0.1% mercuric chloride solution for disinfection for 6 minutes, and then washed with sterile water for 5 times to obtain disinfected seeds; the disinfected seeds were soaked in clean water for 18 hours to obtain pretreated seeds; the pretreated seeds were placed in a culture dish covered with two layers of filter paper, sprinkled with water to soak the filter paper, and then placed in an incubator for germination treatment at 25°C and dark conditions until the seeds turned white to obtain germinated vetiver seeds; peat soil and coconut bran were mixed in a volume ratio of 1:2 to obtain a matrix, the matrix was placed in an autoclave at 121°C for 15 minutes, and then Glomus mosseae was added in a mass ratio of matrix: Glomus mosseae = 50:1 and mixed evenly to obtain a matrix inoculated with arbuscular mycorrhizal fungi; then the germinated plant seeds were mixed in a mass ratio of 1:40 to the matrix inoculated with arbuscular mycorrhizal fungi = 0.5 kg / m 2 The amount of sowing;

[0072] (4) After the planted vetiver grass matures, remove it by roots, and then repeat the planting of vetiver grass according to the method in step (3) until the heavy metal ion content in the soil meets the standard of "Soil Environmental Quality Agricultural Land Soil Risk Control Standard (Trial)" (GB15618-2018), and the restored garden soil is obtained, and garden plants can be planted according to conventional methods.

[0073] Experiment: Garden soil restoration experiment

[0074] 1. Experimental preparation: The repair agents prepared in Example 1 and Comparative Examples 1-6 were used for garden soil repair experiments. The experiment was carried out at the rose garden experimental base in TEDA Street, Binhai New Area, Tianjin. The block area was divided into the experimental area. Before the experiment, the initial contents of cadmium, copper and lead in the soil of the experimental area were determined. Then, the experimental area was divided into 12 small areas, each with an area of ​​3×3m, corresponding to the experimental group 1, the control group 1-10 and the blank control group, respectively.

[0075] 2. Experimental methods:

[0076] Experimental group 1: using the repair agent prepared in Example 1 and the repair method of Example 4;

[0077] Control groups 1-6: using the repairing agents of comparative examples 1-6 and the repairing method of embodiment 4 respectively;

[0078] Control group 7: The repair agent of Example 1 was used. During soil repair, the soil pH was not adjusted in step (1), and the remaining steps were carried out according to the method of Example 4.

[0079] Control group 8: The repair agent of Example 1 was used. During soil repair, Glomus mosseae was not inoculated into the matrix. The matrix and the germinated seeds were directly mixed and sown. The remaining steps were carried out according to the method of Example 4.

[0080] Control group 9: In control group 9, no repair agent was applied during soil repair, but clean water was applied, and the remaining steps were carried out according to the method of Example 4.

[0081] Control group 10: When the control group 10 performed soil remediation, the soil pH was not adjusted after the remediation agent was applied in step (2), and the remaining steps were carried out according to the method of Example 4.

[0082] Blank control group: The blank control group directly cleaned the soil, tilled it, and sowed the germinated seeds, as follows:

[0083] (1) After removing weeds and impurities from the soil, the soil was tilled to a depth of about 35 cm and left to stand for 8 days;

[0084] (2) Vetiver seeds were soaked in 75% ethanol solution for 30 seconds, then placed in 0.1% mercuric chloride solution for disinfection for 6 minutes, and then washed with sterile water for 5 times to obtain disinfected seeds; the disinfected seeds were soaked in clean water for 18 hours to obtain pre-treated seeds; the pre-treated seeds were placed in a culture dish covered with two layers of filter paper, the filter paper was soaked with water, and then placed in an incubator, and germinated at 25°C and dark conditions until the seeds turned white to obtain germinated vetiver seeds; peat soil and coconut bran were mixed in a volume ratio of 1:2 to obtain a matrix, the matrix was placed in an autoclave at 121°C for 15 minutes, and the germinated plant seeds: matrix were mixed in a mass ratio of 1:40, and then 0.5 kg / m 2 amount for sowing.

[0085] (3) Result detection: Five months after the vetiver was sown, the vetiver in each group was uprooted, the soil around the roots was removed and the weight of the vetiver in each group was weighed. The cadmium, copper and lead contents in the soil were measured again. The data are shown in Table 1:

[0086] Table 1

[0087]

[0088]

[0089] According to the data analysis in Table 1:

[0090] (1) After vetiver was planted in the heavy metal contaminated soil in Experimental Group 1, the vetiver grew well and had a high biomass. In addition, the cadmium, copper and lead contents in the soil were significantly reduced. This indicates that the method of the present invention can remove heavy metal ions in the soil relatively quickly and effectively, has a good effect on the restoration of heavy metal contaminated garden soil, and provides a good environment for the growth of garden plants.

[0091] (2) In the control group 1, the chitosan was not treated by the repair agent, and the prepared repair agent had strong permeability and penetrated downward, thereby reducing the fixation effect of the repair agent on heavy metal ions in the soil, and the heavy metal ions in the soil migrated, resulting in a decrease in the amount of plant absorption and enrichment; while in the experimental group 1, the chitosan solution prepared by the repair agent after modifying the chitosan gelled due to the change in temperature after entering the soil, which enhanced the fixation of heavy metal ions and inhibited the migration of heavy metal ions. As a result, the amount of plant absorption and enrichment increased, and the repair effect was relatively good;

[0092] (3) In the preparation of the repair agents in control group 2 and control group 3, dithiothreitol and L-asparagine were not added, respectively. Therefore, the adsorption activity of the nano-silica in the repair agents in control group 3 and control group 4 for heavy metal ions in the soil was consistent. After the arbuscular mycorrhizal fungi secreted organic acids, the adsorbed heavy metal ions were released in large quantities at the same time, causing stress to the plants, reducing the plant biomass and also reducing the repair effect. In experimental group 1, dithiothreitol and L-asparagine were used to modify the nano-silica, respectively, and groups with different heavy metal ion binding abilities were introduced, respectively. Then, under the competitive binding of the secreted organic acids, the bound and fixed heavy metal ions were released successively, eliminating the heavy metal ion stress and improving the absorption and enrichment effect of the plants.

[0093] (4) In the control group 8, arbuscular mycorrhizal fungi were not inoculated during soil remediation, and organic acids were not secreted to activate the fixed heavy metal ions. The amount of heavy metal ions absorbed and enriched by plants was small. After the degradation of the remediation agent, a large amount of heavy metal ions were released. Therefore, the heavy metal ion content in the soil did not decrease significantly.

[0094] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention. The techniques, shapes, and structural parts not described in detail in the present invention are all known technologies.

Claims

1. A method for repairing garden contaminated soil, characterized in that: The method comprises the following steps: (1) After removing weeds and impurities from the soil, plow the soil, adjust the soil pH to 4.5-5.5, and leave it to stand for 5-10 days; (2) At 9-10 am on a sunny day, apply 0.1-0.3 kg / m 2 Spray the repair agent on the soil in the amount of 1000 mg / kg, and plough the soil to a depth of 20-30 cm 4 hours after spraying. After ploughing, spray the repair agent for the second time in the same amount. Adjust the soil pH to 6-7 3-6 days after applying the repair agent. (3) adding the super-enriched plant seeds after germination to the substrate inoculated with arbuscular mycorrhizal fungi, mixing evenly and then sowing; (4) After the hyperaccumulator plants are mature, they are uprooted and then the hyperaccumulator plants are repeatedly planted according to the method in step (3) until the heavy metal ion content in the soil meets the national standard to obtain restored garden soil.

2. The method for repairing garden contaminated soil according to claim 1, characterized in that: The repair agent in step (2) comprises the following raw materials: Chitosan, 50wt% isopropanol aqueous solution, 1,2-butylene oxide, nano silicon dioxide, L-asparagine and dithiothreitol.

3. A method for repairing garden contaminated soil according to claim 2, characterized in that: The preparation method of the repair agent is as follows: A: Add chitosan to 50wt% isopropanol aqueous solution and stir to disperse, let stand for 2-6h, then add 1,2-butylene oxide, stir at room temperature for 1h, then heat to 60-70℃ and continue to react for 20-40min, filter to remove the filtrate after the reaction is completed, and then dry at 45℃ to obtain modified chitosan; B: Add nano-silica into water and stir to disperse, heat to 60-80°C and keep warm for 1-2 hours, then add dithiothreitol and react at constant temperature for 30-60 minutes, then cool to 40-50°C and add L-asparagine to react for 1-2 hours, after the reaction is completed, filter to remove the filtrate and place at 4°C for cold treatment overnight to obtain pre-treated nano-silica; C: Add water to the modified chitosan to prepare a 2 wt% modified chitosan solution, add the pretreated nano-silicon dioxide, mix well, and then let stand at 4°C for 12-24 hours to obtain a repair agent.

4. The method for repairing garden contaminated soil according to claim 3, characterized in that: In the step A, the mass ratio of chitosan, 50 wt% isopropanol aqueous solution and 1,2-butylene oxide is (0.5-1): (5-10): (0.2-0.5).

5. The method for repairing garden contaminated soil according to claim 4, characterized in that: In the step B, the mass ratio of nano-silicon dioxide, dithiothreitol and L-asparagine is (2-4): (0.2-0.5): (0.1-0.2).

6. The method for repairing garden contaminated soil according to claim 5, characterized in that: In the step C, the mass ratio of the 2 wt % modified chitosan solution to the pretreated nano-silicon dioxide is (5-10): (2-4).

7. The method for remediating garden contaminated soil according to claim 6, characterized in that: The super-accumulator plant in the step is any one of vetiver and centipede grass.

8. The method for remediating garden contaminated soil according to claim 7, characterized in that: The super-enriched plant seed germination operation in step (3) is specifically as follows: The super-accumulator plant seeds were soaked in 75% ethanol solution for 30 seconds, then placed in 0.1% mercuric chloride solution for 5-8 minutes for disinfection, and then washed with sterile water for 5 times to obtain disinfected seeds; Soak the sterilized seeds in clean water for 12-24 hours to obtain pretreated seeds; The pretreated seeds were placed in a culture dish covered with two layers of filter paper, and the filter paper was soaked with water and placed in an incubator for germination at 25°C in darkness until the seeds turned white to obtain super-enriched plant seeds after germination.

9. The method for remediating garden contaminated soil according to claim 8, characterized in that: The specific operation of inoculating the matrix with arbuscular mycorrhizal fungi in step (3) is as follows: Peat soil and coconut bran were mixed at a volume ratio of 1:2 to obtain a matrix, and arbuscular mycorrhizal fungi were mixed at a mass ratio of matrix:arbuscular mycorrhizal fungi=50:1 to obtain a matrix inoculated with arbuscular mycorrhizal fungi.

10. The method for remediating garden contaminated soil according to claim 9, characterized in that: The arbuscular mycorrhizal fungus is Glomus mosseae.

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