Biochemical synergistic remediation method for heavy metal contaminated soil

Abstract

The invention relates to the technical field of environmental remediation, and discloses a biochemical synergistic remediation method for heavy metal contaminated soil, which comprises the following steps: S1, sampling the heavy metal contaminated soil, and analyzing the type, concentration and occurrence form of heavy metals of the heavy metal contaminated soil; s2, extracting active ingredients of polyphenols, organic acids or alkaloids from the plant materials; s3, applying a plant source activating agent to regulate the chemical form of the heavy metal in the soil and promote the activation of the heavy metal; s4, inoculating a functional microbial agent to enhance the heavy metal immobilization, transformation and phytoremediation capabilities; s5, planting hyperaccumulators, and cooperatively using the plant extract, the plant source activator and the microbial agent; s6, plant residue treatment and soil improvement. Through the synergistic effect of the plant extract, the plant source activator, the microbial agent and the hyperaccumulator, the plant source activator, the microbial agent and the hyperaccumulator can jointly act on the heavy metal contaminated soil from multiple ways, and chelating, activating, degrading and fixing of heavy metal are rapidly achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental restoration, and in particular to a biochemical synergistic restoration method for heavy metal contaminated soil. Background Art

[0002] Heavy metal contaminated soil is one of the major environmental problems facing the world today, mainly from industrial waste, mining, smelting, electroplating, excessive use of agricultural fertilizers and pesticides, etc. Heavy metals in the soil (such as cadmium, lead, copper, zinc, etc.) are highly toxic, difficult to degrade and easy to accumulate. Once entering the soil, they will cause serious harm to the ecosystem and human health through migration and accumulation. Once this kind of pollution is formed, it is difficult to repair and the cycle is long. It has become an important bottleneck restricting ecological environment governance and sustainable development.

[0003] In the existing technology, a single remediation technology (such as physical, chemical or biological remediation) has obvious limitations when dealing with heavy metal contaminated soil: physical remediation can usually only isolate or remove contaminated soil, but cannot improve soil properties and is costly; although chemical remediation reacts quickly, it is easy to cause secondary pollution, and long-term use may damage soil structure; and biological remediation is limited by pollution concentration and biological tolerance, and has low efficiency and long cycles in high-concentration pollution environments. These methods lack a synergistic mechanism and are difficult to comprehensively and efficiently solve the problem of soil heavy metal pollution. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a biochemical synergistic remediation method for heavy metal contaminated soil, which solves the problem that the existing single remediation technology (such as physical, chemical or biological remediation) has obvious limitations in treating heavy metal contaminated soil.

[0005] To achieve the above objectives, the present invention is implemented by the following technical scheme: a biochemical synergistic remediation method for heavy metal contaminated soil, comprising the following steps:

[0006] S1. Pollution Assessment

[0007] Sampling heavy metal contaminated soil to analyze the types, concentrations and occurrence forms of heavy metals, as well as the basic physical and chemical properties of the soil;

[0008] S2. Preparation and use of plant extracts

[0009] Extracting polyphenols, organic acids or alkaloids active ingredients from plant materials, wherein the plant extracts are applied directly or mixed with organic fertilizers for soil conditioning;

[0010] S3. Application of plant-derived activators

[0011] Apply plant-derived activators to adjust the chemical forms of heavy metals in the soil and promote the activation of heavy metals;

[0012] S4. Inoculation of microbial agents

[0013] Inoculate functional microbial agents to enhance heavy metal fixation, transformation and phytoremediation capabilities;

[0014] S5. Phytoremediation

[0015] Planting super-enriched plants and combining them with plant extracts, plant-derived activators and microbial agents;

[0016] S6. Plant residue treatment and soil improvement

[0017] The restored hyperaccumulators are harvested, plant residues are processed centrally, and organic fertilizers containing plant extracts are applied to the restored soil to restore soil fertility.

[0018] Preferably, in step S2, the plant material includes tea leaves, liquorice, coptis root, gardenia or eucommia, and the plant extract is prepared by water extraction, alcohol extraction or a composite extraction method combined with ultrasonic extraction.

[0019] Preferably, in step S2, the plant extract is used in the following manner:

[0020] S201, diluting the plant extract to a concentration of 1%-5% and applying it directly to the soil;

[0021] S202, mixing the plant extract with organic fertilizer in a ratio of 1:20 to 1:50 and applying the mixture to the heavy metal contaminated soil;

[0022] S203, preparing plant-derived fertilizer by fermentation, fermenting plant extract with lactic acid bacteria or yeast for 5-15 days and then applying.

[0023] Preferably, in step S3, main components of the plant-derived activator include organic acids, polyphenols and polysaccharides, wherein the organic acid is citric acid or oxalic acid, the polyphenols are tea polyphenols or tannic acid, and the polysaccharide is gum arabic.

[0024] Preferably, in the step S3, the plant-derived activator is applied to the soil by spraying or root irrigation, and the single application amount is 20-50 mL per square meter.

[0025] Preferably, in the step S4, the microbial agent includes detoxification functional bacteria and growth-promoting functional bacteria, the detoxification functional bacteria include Pseudomonas or yeast, and the growth-promoting functional bacteria include Rhizobium or Bacillus.

[0026] Preferably, in step S5, the superaccumulator plants include Indian mustard, sunflower, water spinach, metal grass or yarrow, and the corresponding plants are selected according to the types of heavy metals in the contaminated soil.

[0027] Preferably, in the step S5, when the plant extract and the microbial agent are mixed to prepare the plant-derived fertilizer, they are mixed in a ratio of 1:2 to 1:10 and then applied, and the application amount is 0.5-2 kg per square meter of soil.

[0028] Preferably, in the step S6, the plant residues are incinerated after harvesting, and the ash produced after incineration is centrally processed to recover heavy metals and prevent secondary pollution.

[0029] Preferably, in the step S6, after the restoration is completed, the soil is improved by applying an organic fertilizer containing a plant extract, wherein the organic fertilizer is made by fermenting the plant extract with animal manure or straw.

[0030] The present invention provides a biochemical synergistic remediation method for heavy metal contaminated soil.

[0031] Beneficial effects:

[0032] 1. The present invention can act on heavy metal contaminated soil from multiple pathways through the synergistic effect of plant extracts, plant-derived activators, microbial agents and hyperaccumulators, and quickly achieve chelation, activation, degradation and fixation of heavy metals. Compared with traditional single remediation technology, this multi-pathway synergistic mechanism significantly improves the remediation efficiency and shortens the remediation time.

[0033] 2. The plant extracts and plant-derived activators of the present invention are all derived from natural plant materials, which are non-toxic and harmless, avoiding the secondary pollution that may be caused by traditional chemical remediation technology. At the same time, these natural materials will gradually degrade in the soil, will not cause additional burden on the ecosystem, and will help to restore the ecological safety of the area.

[0034] 3. The plant-derived activator of the present invention regulates the chemical forms of heavy metals in the soil through active ingredients such as organic acids and polyphenols, promotes the transformation of heavy metals from insoluble forms to mobile forms, and creates conditions for the absorption and degradation of hyperaccumulators and microorganisms. This process not only improves the remediation efficiency, but also provides a healthier physical and chemical environment for the soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a flow chart of the biochemical synergistic remediation method for heavy metal contaminated soil. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Please see attached Figure 1 The present invention provides a biochemical synergistic remediation method for heavy metal contaminated soil, comprising the following steps:

[0038] S1. Pollution Assessment

[0039] Sampling heavy metal contaminated soil to analyze the types, concentrations and occurrence forms of heavy metals, as well as the basic physical and chemical properties of the soil;

[0040] S2. Preparation and use of plant extracts

[0041] Extraction of polyphenolic, organic acid or alkaloid active ingredients from plant materials, and application of plant extracts for soil conditioning either directly or after mixing with organic fertilizers;

[0042] S3. Application of plant-derived activators

[0043] Apply plant-derived activators to adjust the chemical forms of heavy metals in the soil and promote the activation of heavy metals;

[0044] S4. Inoculation of microbial agents

[0045] Inoculate functional microbial agents to enhance heavy metal fixation, transformation and phytoremediation capabilities;

[0046] S5. Phytoremediation

[0047] Planting super-enriched plants and combining them with plant extracts, plant-derived activators and microbial agents;

[0048] S6. Plant residue treatment and soil improvement

[0049] The restored hyperaccumulators are harvested, plant residues are processed centrally, and organic fertilizers containing plant extracts are applied to the restored soil to restore soil fertility.

[0050] Specifically, S1. Pollution assessment

[0051] By collecting soil samples, standard testing equipment such as atomic absorption spectrometer (AAS) or inductively coupled plasma mass spectrometer (ICP-MS) is used to analyze the types and concentrations of heavy metals in the soil, and to identify the main heavy metal pollutants in the contaminated soil (such as cadmium, lead, copper, etc.). At the same time, the BCR continuous extraction method is combined to determine the occurrence form of heavy metals and analyze their active state ratio to provide a scientific basis for the selection of remediation strategies. In addition, the physical and chemical parameters of the soil (such as pH, organic matter content and porosity) are also tested to adjust the dosage and strategy of subsequent remediation materials.

[0052] S2. Preparation and use of plant extracts

[0053] The plant extracts of the present invention are of natural origin, mainly selected from plant materials rich in polyphenols, organic acids and alkaloids, such as tea, licorice, coptis root, etc. These ingredients have good heavy metal chelating ability and soil conditioning ability. The extraction methods include:

[0054] Water extraction method: Crush the dried tea leaves and add hot water (90-100°C) at a mass-to-volume ratio of 1:20. Extract for 2 hours and filter to obtain a liquid extract.

[0055] Alcohol extraction method: Use 70% ethanol as solvent to soak the plant material for 48 hours to extract polyphenols.

[0056] Fermentation to prepare plant-derived fertilizer: The extract is mixed with lactic acid bacteria or yeast for fermentation to prepare a plant-derived fertilizer containing organic matter and heavy metal chelators.

[0057] The extract can be used flexibly. It can be diluted into a 1%-5% aqueous solution and sprayed directly on the soil, or mixed with organic fertilizer in a ratio of 1:20 to 1:50. It can not only activate and adsorb heavy metals, but also improve soil fertility.

[0058] S3. Application of plant-derived activators

[0059] Plant-based activators are mainly composed of natural organic acids such as citric acid and tannic acid, and can be applied to contaminated soil by root irrigation or spraying. The function of the activator is to increase the bioavailability of heavy metals, enhance the absorption capacity of subsequent plants and microorganisms, and improve soil structure to reduce the risk of heavy metal migration.

[0060] S4. Inoculation of microbial agents

[0061] The bacterial agent includes detoxification functional bacteria and growth-promoting functional bacteria, such as Pseudomonas, yeast and Bacillus. The detoxification functional bacteria can decompose or fix heavy metals in the soil, while the growth-promoting functional bacteria enhance the plant's ability to absorb heavy metals by secreting plant hormones or organic acids. The bacterial agent can be mixed with plant-derived fertilizers and then applied, or it can be inoculated into the soil by spraying alone.

[0062] S5. Phytoremediation

[0063] The selection of hyperaccumulators is based on the types of major heavy metals in the soil. Cadmium pollution is suitable for growing Indian mustard, lead pollution is suitable for growing sunflower, and copper pollution is suitable for growing yarrow. The application of plant extracts and activators during the growth of plants helps to promote the enrichment of heavy metals in plants, while improving the stress resistance and repair effects of plants.

[0064] S6. Plant residue treatment and soil improvement

[0065] During the phytoremediation process, the above-ground parts are harvested regularly to avoid the accumulation of heavy metals in the plant body. The harvested plant residues can be incinerated to recover the heavy metals in the residues. After the restoration is completed, in order to restore soil fertility, traditional Chinese medicine organic fertilizer combined with plant extracts can be applied to improve soil quality.

[0066] In step S2, the plant material includes tea leaves, liquorice, coptis root, gardenia or eucommia, and the plant extract is prepared by water extraction, alcohol extraction or a composite extraction method combined with ultrasonic extraction.

[0067] Specifically, the preparation of plant extracts makes full use of the active ingredients rich in natural plant materials, the main components of which include polyphenols (such as tea polyphenols, flavonoids), organic acids (such as citric acid, oxalic acid) and alkaloids (such as glycyrrhizic acid). Taking tea extraction as an example, the tea leaves are crushed and added to 90°C hot water at a ratio of 1:20 for extraction for 2 hours. The resulting filtrate has good heavy metal adsorption capacity. The extract can be used directly for soil repair or further processed to prepare plant-based fertilizers.

[0068] In step S2, the plant extracts are used in the following ways:

[0069] S201, diluting the plant extract to a concentration of 1%-5% and applying it directly to the soil;

[0070] S202, mixing the plant extract with organic fertilizer in a ratio of 1:20 to 1:50 and applying the mixture to the heavy metal contaminated soil;

[0071] S203, preparing plant-derived fertilizer by fermentation, fermenting plant extract with lactic acid bacteria or yeast for 5-15 days and then applying.

[0072] Specifically, the three ways of using plant extracts correspond to different repair scenarios:

[0073] Direct application: In lightly polluted soils, the extract can be diluted and sprayed directly on the soil surface to quickly activate heavy metals and achieve plant absorption.

[0074] Mixed with organic fertilizer: Suitable for medium to severe polluted soils. It can be mixed with organic fertilizer to chelate heavy metals and replenish soil nutrients.

[0075] Fermentation to prepare fertilizer: For heavily polluted soil, it can be fermented to prepare fertilizer rich in bacteria, thus improving the soil microecological environment.

[0076] In step S3, main components of the plant-derived activator include organic acids, polyphenols and polysaccharides, wherein the organic acid is citric acid or oxalic acid, the polyphenols are tea polyphenols or tannic acid, and the polysaccharide is gum arabic.

[0077] Specifically, the core ingredients of plant-derived activators include:

[0078] Organic acids: such as citric acid, used to dissolve heavy metal precipitates in the soil.

[0079] Polyphenols: such as tea polyphenols, can fix heavy metals through chelation.

[0080] Polysaccharides: such as gum arabic, used to enhance soil aggregate stability.

[0081] These ingredients are compounded in scientific proportions and applied to the soil, which can significantly improve the mobility of heavy metals and microbial activity in the soil.

[0082] In step S3, the plant-derived activator is applied into the soil by spraying or root irrigation, with a single application amount of 20-50 mL per square meter.

[0083] Specifically, the activator is applied by spraying or root irrigation, and the dilution concentration is controlled at 1%-2%. 20-50mL is applied per square meter of soil, and the dosage can be adjusted according to the degree of pollution, which can ensure the activation effect and avoid causing additional pressure on the soil environment.

[0084] In step S4, the microbial agent includes detoxification functional bacteria and growth-promoting functional bacteria, the detoxification functional bacteria include Pseudomonas or yeast, and the growth-promoting functional bacteria include Rhizobia or Bacillus.

[0085] Specifically, detoxification bacteria mainly include Pseudomonas and yeast, which secrete organic acids that can form stable complexes with heavy metals to reduce the biological toxicity of heavy metals. Growth-promoting bacteria such as Bacillus and Rhizobium can improve the tolerance of plants to heavy metal stress by secreting plant hormones such as IAA (indoleacetic acid).

[0086] In step S5, the hyperaccumulator plants include Indian mustard, sunflower, water spinach, metal grass or yarrow, and the corresponding plants are selected according to the types of heavy metals in the contaminated soil.

[0087] Specifically, hyperaccumulators such as Indian mustard, sunflower and metal grass have strong root absorption capacity for heavy metals and are suitable for different types of heavy metal contaminated soils. The planting density is 200-400 plants / m 2 , combined application of plant extracts and activators during growth can further improve the repair efficiency.

[0088] In step S5, when the plant extract and the microbial agent are mixed to prepare the plant-derived fertilizer, they are mixed in a ratio of 1:2 to 1:10 and then applied, with the application amount being 0.5-2 kg per square meter of soil.

[0089] Specifically, the mixing ratio of plant extract and microbial agent is adjusted to 1:2 to 1:10. For example, 1L of tea extract can be mixed with 2-10L of lactic acid bacteria agent, and the plant-derived fertilizer is prepared after fermentation for 5-15 days. This kind of fertilizer is particularly suitable for severely polluted soil, and the synergistic effect of microorganisms and plant extracts can significantly improve the remediation effect.

[0090] In step S6, the plant residues are incinerated after harvesting, and the ash produced after incineration is centrally processed to recover heavy metals and prevent secondary pollution.

[0091] Specifically, the hyper-enriched plant residues are incinerated after harvesting, and the incineration temperature is controlled at 500℃-700℃, which can effectively recover heavy metal ash for subsequent industrial extraction or safe landfill.

[0092] In step S6, after the restoration is completed, the soil is improved by applying organic fertilizer containing plant extracts, where the organic fertilizer is made by fermenting the plant extracts with animal manure or straw.

[0093] Specifically, after the restoration is completed, organic fertilizer containing plant extracts is applied. It can be made by mixing plant extracts, animal manure and straw for fermentation. The fermentation cycle is 15-20 days and is used to improve soil structure and restore soil fertility.

[0094] The following is an introduction in conjunction with specific embodiments:

[0095] Example 1: Remediation of Cadmium-Contaminated Soil

[0096] Site Background

[0097] The soil of an industrial site was contaminated with cadmium, with a cadmium concentration of 3.5 mg / kg, far higher than the risk screening value for soil cadmium contamination (1.0 mg / kg). The soil pH was 5.8, which was acidic soil, and heavy metal cadmium was mainly in ionic and exchangeable states.

[0098] Implementation steps

[0099] S1: Contamination Assessment

[0100] Soil samples were collected from the site and the cadmium concentration was detected by inductively coupled plasma mass spectrometry (ICP-MS). The BCR continuous extraction method was used to determine the occurrence form of cadmium. The results showed that 60% of the cadmium in the soil was in an exchangeable state.

[0101] S2: Preparation and use of plant extracts

[0102] Licorice was selected as the plant material, which was crushed and mixed with 70% ethanol at a ratio of 1:20, extracted at room temperature for 48 hours, and filtered to obtain a liquorice alcohol extract.

[0103] The liquorice extract was diluted to a concentration of 3% and then evenly mixed with organic fertilizer at a ratio of 1:30 to prepare a compound fertilizer, and 1 kg was applied per square meter of soil as a base fertilizer.

[0104] S3: Application of plant-derived activators

[0105] A plant-derived activator was prepared, the main ingredients of which were citric acid, tannic acid and gum arabic. The activator was diluted into a 1% aqueous solution and 30 mL was sprayed per square meter of soil to activate the heavy metal cadmium in the soil and promote its migration to the plant root system.

[0106] S4: Inoculation of microbial agents

[0107] Pseudomonas putida was used as the detoxification functional bacteria and Bacillus subtilis was used as the growth-promoting functional bacteria. The concentration of live bacteria in the bacterial agent was 1×10 8 CFU / mL in liquid form was sprayed on the soil surface, with 0.5L applied per square meter.

[0108] The application of microbial agents is separated by one week from the application of activators and compound fertilizers to ensure the synchronous action of heavy metal activation and microorganisms.

[0109] S5: Phytoremediation

[0110] Indian mustard (Brassica juncea) was planted at a density of 250 plants per square meter. During the growth period, a diluted solution of licorice extract (concentration of 2%) was applied every 2 weeks to enhance the plant's ability to absorb cadmium.

[0111] S6: Plant residue treatment and soil improvement

[0112] The above-ground parts of Indian mustard are harvested every quarter, and the plant residues are burned at a controlled temperature of 600°C. The ash is then processed centrally to recover heavy metals.

[0113] After the restoration is completed, organic fertilizer made from fermented liquorice extract and animal manure is applied at a rate of 2 kg per square meter of soil to restore soil fertility.

[0114] Results and Analysis

[0115] After one year of restoration, the total concentration of cadmium in the soil was reduced from 3.5mg / kg to 0.9mg / kg, and the proportion of exchangeable cadmium was reduced by more than 70%, reaching the safety standard. At the same time, the pH value of the soil was increased to 6.3, and the fertility was significantly improved, making it suitable for agricultural use.

[0116] Beneficial Effects

[0117] Through the synergistic effects of plant extracts, plant-derived activators, microbial agents and hyperaccumulators, the concentration of heavy metal cadmium in the soil was effectively reduced, and the physical and chemical properties of the soil were improved, achieving an efficient and environmentally friendly restoration effect.

[0118] Example 2: Remediation of lead-contaminated soil

[0119] Site Background

[0120] A certain agricultural land has been polluted by lead-containing wastewater for a long time. The lead concentration in the soil is 120 mg / kg, mainly in the form of carbonate and iron-manganese oxide. The soil is neutral with a pH value of 7.2.

[0121] Implementation steps

[0122] S1: Contamination Assessment

[0123] X-ray fluorescence spectroscopy (XRF) analysis of soil samples revealed a total lead content of 120 mg / kg, of which mobile lead accounted for 40%.

[0124] S2: Preparation and use of plant extracts

[0125] Tea leaves were selected as plant raw materials, and tea polyphenol extract was prepared by water extraction method: the tea leaves were crushed and added with 90°C hot water at a ratio of 1:15, and extracted for 2 hours, and the water extract was obtained after filtering.

[0126] Mix tea polyphenols extract and organic fertilizer in a ratio of 1:25 to prepare compound fertilizer, apply 1.5 kg per square meter, and spread evenly on the soil surface.

[0127] S3: Application of plant-derived activators

[0128] Prepare a plant-derived activator, the main ingredients of which include oxalic acid, tannic acid and gum arabic, dilute it into a 2% solution, apply 40 mL per square meter, and apply it to the soil by spraying to activate the lead and enhance the efficiency of subsequent plant absorption.

[0129] S4: Inoculation of microbial agents

[0130] Inoculate yeast (Saccharomyces cerevisiae) and rhizobium (Rhizobium spp.), mix the bacterial agents in a 1:1 ratio and spray them, apply 0.8L per square meter, and apply them at intervals with plant-based activators.

[0131] S5: Phytoremediation

[0132] Sunflowers (Helianthus annuus) were planted at a density of 300 plants per square meter. During this period, diluted tea polyphenol extract (concentration of 3%) was sprayed every 3 weeks to improve the stress resistance and absorption capacity of the plants.

[0133] S6: Plant residue treatment and soil improvement

[0134] After the growth cycle is over, the above-ground parts of the sunflowers are harvested and the residues are incinerated. The incineration temperature is controlled at 700°C, and the lead ash residue after incineration is collected and disposed of centrally.

[0135] After the restoration is completed, fermented plant-derived fertilizer is applied to the soil at a rate of 2.5 kg per square meter to improve the physical and chemical properties of the soil and restore its agricultural use.

[0136] Results and Analysis

[0137] Six months after restoration, the concentration of lead in the soil dropped from 120 mg / kg to 50 mg / kg, the proportion of carbonate-bound and iron-manganese oxide-bound lead decreased significantly, and the ecological risk of soil lead was significantly reduced. At the same time, the soil structure was improved, the soil porosity increased, and the organic matter content increased.

[0138] Beneficial Effects

[0139] The combined use of plant extracts, activators, microbial agents and sunflower effectively reduced the lead pollution level in the soil and restored the soil's productivity. At the same time, the incineration of plant residues achieved the safe recovery of heavy metals.

[0140] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A biochemical synergistic remediation method for heavy metal contaminated soil, characterized in that: The following steps are involved: S1. Pollution Assessment Sampling heavy metal contaminated soil to analyze the types, concentrations and occurrence forms of heavy metals, as well as the basic physical and chemical properties of the soil; S2. Preparation and use of plant extracts Extracting polyphenols, organic acids or alkaloids active ingredients from plant materials, wherein the plant extracts are applied directly or mixed with organic fertilizers for soil conditioning; S3. Application of plant-derived activators Apply plant-derived activators to adjust the chemical forms of heavy metals in the soil and promote the activation of heavy metals; S4. Inoculation of microbial agents Inoculate functional microbial agents to enhance heavy metal fixation, transformation and phytoremediation capabilities; S5. Phytoremediation Planting super-enriched plants and combining them with plant extracts, plant-derived activators and microbial agents; S6. Plant residue treatment and soil improvement The restored hyperaccumulators are harvested, plant residues are processed centrally, and organic fertilizers containing plant extracts are applied to the restored soil to restore soil fertility.

2. The biochemical synergistic remediation method for heavy metal contaminated soil according to claim 1, characterized in that: In the step S2, the plant material includes tea leaves, liquorice, coptis root, gardenia or eucommia, and the plant extract is prepared by water extraction, alcohol extraction or a composite extraction method combined with ultrasonic extraction.

3. The biochemical synergistic remediation method for heavy metal contaminated soil according to claim 1, characterized in that: In the step S2, the plant extract is used in the following manner: S201, diluting the plant extract to a concentration of 1%-5% and applying it directly to the soil; S202, mixing the plant extract with organic fertilizer in a ratio of 1:20 to 1:50 and applying the mixture to the heavy metal contaminated soil; S203, preparing plant-derived fertilizer by fermentation, fermenting plant extract with lactic acid bacteria or yeast for 5-15 days and then applying.

4. The biochemical synergistic remediation method for heavy metal contaminated soil according to claim 1, characterized in that: In the step S3, the main components of the plant-derived activator include organic acids, polyphenols and polysaccharides, wherein the organic acid is citric acid or oxalic acid, the polyphenols are tea polyphenols or tannic acid, and the polysaccharide is gum arabic.

5. The biochemical synergistic remediation method for heavy metal contaminated soil according to claim 1, characterized in that: In the step S3, the plant-derived activator is applied to the soil by spraying or root irrigation, with a single application amount of 20-50 mL per square meter.

6. The biochemical synergistic remediation method for heavy metal contaminated soil according to claim 1, characterized in that: In the step S4, the microbial agent includes detoxification functional bacteria and growth-promoting functional bacteria, the detoxification functional bacteria include Pseudomonas or yeast, and the growth-promoting functional bacteria include Rhizobium or Bacillus.

7. The biochemical synergistic remediation method for heavy metal contaminated soil according to claim 1, characterized in that: In the step S5, the superaccumulator plants include Indian mustard, sunflower, water spinach, metal grass or yarrow, and the corresponding plants are selected according to the types of heavy metals in the contaminated soil.

8. The biochemical synergistic remediation method for heavy metal contaminated soil according to claim 1, characterized in that: In the step S5, when the plant extract and the microbial agent are mixed to prepare the plant-derived fertilizer, they are mixed in a ratio of 1:2 to 1:10 and then applied, and the application amount per square meter of soil is 0.5-2 kg.

9. The biochemical synergistic remediation method for heavy metal contaminated soil according to claim 1, characterized in that: In the step S6, the plant residues are incinerated after harvesting, and the ash produced after incineration is centrally processed to recover heavy metals and prevent secondary pollution.

10. The biochemical synergistic remediation method for heavy metal contaminated soil according to claim 1, characterized in that: In the step S6, after the restoration is completed, the soil is improved by applying an organic fertilizer containing plant extracts, wherein the organic fertilizer is made by fermenting the plant extracts with animal manure or straw.

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