A composite conditioning module for remediation of heavy metal pollution in acid soil and a time-sequential accurate remediation method for heavy metal pollution in acid soil

Abstract

The present application belongs to the technical field of soil remediation, and particularly relates to a composite conditioning module for remediation of heavy metal pollution in acid soil and a time-sequential precise remediation method for heavy metal pollution in acid soil. The present application carries out time-sequential precise remediation of heavy metal pollution in acid soil based on the composite conditioning module, which specifically reflects that a first module composition is applied to carry out physical and chemical passivation, to preliminarily stabilize heavy metals and adjust pH; after 7-10 days, a second module composition is applied to carry out organic complexing and structure modification, to further passivate and improve soil physical structure; after 3-5 days, microbial inoculants are inoculated, to enable strains to quickly colonize and proliferate in the good environment created in the previous step; and finally, hyperaccumulation plants are planted to extract and remove. The remediation method solves the antagonism problem in multi-component remediation and realizes synergistic effect through precise time-sequential control.

Description

Technical Field

[0001] This invention belongs to the field of soil remediation technology, specifically relating to a composite conditioning module for the remediation of heavy metal pollution in acidic soil and a time-series precise remediation method for heavy metal pollution in acidic soil. Background Technology

[0002] Heavy metal pollution in soil is a global environmental problem, mainly manifested as the accumulation of heavy metals (such as cadmium, lead, arsenic, and mercury) in soil exceeding safe thresholds, leading to soil degradation, crop contamination, and health risks. Heavy metal pollution is particularly prominent in mineral-rich areas. Furthermore, in some heavily polluted areas, in addition to combined cadmium, lead, and arsenic pollution, the soil is often acidic (pH 4.5–6.0) and has high background calcium and magnesium content, further increasing the difficulty of remediation.

[0003] Existing remediation technologies mainly include physical remediation, chemical remediation, and bioremediation, but all have significant drawbacks. Physical remediation primarily employs measures such as soil removal, soil replacement, topsoil removal, soil introduction, and deep tillage, which are costly and damage soil structure. Chemical remediation mainly includes the application of chemical passivating agents, chemical leaching, and in-situ chemical reduction techniques. However, while applying lime can increase soil pH, its effects are unstable and can easily lead to soil compaction; phosphate passivating agents may cause phosphorus eutrophication; and biochar alone has limited effectiveness against variable-valence heavy metals such as arsenic. Bioremediation of soil heavy metals mainly includes phytoremediation, microbial remediation, and animal remediation. However, bioremediation is time-consuming, highly susceptible to environmental conditions, prone to secondary pollution, and carries the risk of food chain transmission.

[0004] The current mainstream remediation method is to mix and apply multiple passivating materials at once. Although it has a certain effect on the remediation of heavy metals in soil, it still has inherent defects: First, component antagonism: components with different physicochemical properties can interfere with each other. For example, inorganic passivating agents can increase the pH, which can lead to the inactivation of subsequently applied microbial agents. Second, temporal contradiction: phytoremediation requires heavy metals to have a certain degree of bioavailability for absorption, while passivation remediation aims to reduce bioavailability, and the two goals are contradictory. Third, short-lived effect: a single large-dose application may cause damage to soil structure or secondary pollution, and the effect is not lasting.

[0005] Therefore, developing a time-sequential repair method that can coordinate different repair mechanisms and follow the laws of reaction kinetics is the key to solving the above-mentioned technical bottlenecks. Summary of the Invention

[0006] The purpose of this invention is to provide a composite conditioning module for the remediation of heavy metal pollution in acidic soil and a time-series precise remediation method for heavy metal pollution in acidic soil. The composite conditioning module can solve the problems of multi-component antagonism, microbial colonization environment optimization and plant extraction efficiency improvement in the existing remediation of heavy metal pollution in acidic soil, and achieve efficient stabilization and removal of heavy metals.

[0007] The present invention also provides a composite conditioning module for the remediation of heavy metal pollution in acidic soil, comprising a first module composition, a second module composition, and a third module composition, each packaged separately. The total weight of the first module composition, the second module composition, and the third module composition is 100%, comprising 60% to 70% of the first module composition, 20% to 30% of the second module composition, and 8% to 10% of the third module composition.

[0008] The first module composition comprises 12%~20% modified tea biochar, 13%~20% modified straw biochar, 10%~15% calcium dihydrogen phosphate, and 15%~20% silicon-calcium-magnesium soil conditioner;

[0009] The second module composition comprises 5%~10% anionic polyacrylamide, 3%~5% polyaspartic acid, 2%~4% polyglutamic acid, 2%~5% hydrolyzed polymaleic anhydride, and 8%~12% mineral-derived potassium humate;

[0010] The third module composition is a compound biological fertilizer, including Bacillus subtilis (Bacillus subtilis (B. subtilis)). Bacillus subtle ) and gelatinous spore-forming bacteria ( Paenibacillus mucilaginosus The effective live bacteria count of the compound biological fertilizer is ≥1 billion CFU / g.

[0011] Preferably, the modified tea biochar has a tea polyphenol content of ≥8.5% and a specific surface area of ​​≥280m². 2 / g; the modified straw biochar includes CO2 modified straw biochar; the silicon-calcium-magnesium soil conditioner mineral powder has a fineness ≥300 mesh, CaO content ≥38%, MgO content ≥8%, SiO2 content ≥28%, and pH 9.5~11.0.

[0012] Preferably, the anionic polyacrylamide has a molecular weight of 12-15 million, the polyaspartic acid has a molecular weight of 8,000-12,000, the polyglutamic acid has a molecular weight of 10,000-15,000, the hydrolysis degree of the hydrolyzed polymaleic anhydride is ≥90%, and the fulvic acid content in the mineral-derived potassium fulvicate is ≥70%.

[0013] This invention also provides the application of the composite conditioning module described above in the time-sequential remediation of heavy metal pollution in acidic soil.

[0014] This invention also provides a time-series precise remediation method for heavy metal pollution in acidic soils, utilizing the composite conditioning module described in the above technical solution for remediation, including a sequential physical and chemical passivation stage, a structural improvement and complexation stage, a biological activation stage, and a plant synergistic extraction stage, comprising the following steps:

[0015] The physical and chemical passivation stage includes: after applying the first module composition to the acidic soil contaminated with heavy metals, deep tilling of the acidic soil contaminated with heavy metals.

[0016] The structural improvement and complexation stage includes: 7 to 10 days after deep plowing, applying the second module composition to the acidic soil contaminated with heavy metals after deep plowing, and then rotary tilling.

[0017] The bioactivation stage includes: 3 to 5 days after rotary tillage, applying the third module composition to the acidic soil contaminated with heavy metals after rotary tillage, performing shallow tillage, and then irrigating to 60% to 70% of field capacity;

[0018] The plant synergistic extraction stage includes: planting hyperaccumulating plants 7-10 days after irrigation, and continuously planting for 3 growth cycles; the hyperaccumulating plants include the following percentages of plants: Sedum aizoon 40%-60%, Centipede grass 20%-30%, and Solanum nigrum 10%-20%.

[0019] Preferably, the application rate of the first module composition is 2.5% to 3.5% of the mass of acidic soil; the application rate of the second module composition is 1.0% to 1.5% of the mass of acidic soil; the application rate of the third module composition is 0.8% to 1.2% of the mass of acidic soil; and the planting density of the hyperaccumulating plants is 3,000 to 4,000 plants per mu.

[0020] Preferably, the depth of deep tillage is 25-30cm; the depth of rotary tillage is 15-20cm; and the depth of shallow tillage is >0cm and ≤10cm.

[0021] Preferably, the remediation of heavy metal pollution in acidic soil includes the reconstruction of acidic soil microbial communities and / or reduction of heavy metal content.

[0022] Preferably, the pH value of the acidic soil is 4.5 to 6.0.

[0023] Preferably, the heavy metal includes one or more of Cd, Pb, As and Hg.

[0024] Beneficial effects:

[0025] This invention provides a composite conditioning module for the remediation of heavy metal pollution in acidic soils and a time-series precise remediation method for heavy metal pollution in acidic soils. Based on the composite conditioning module, this invention performs time-series precise remediation of heavy metal pollution in acidic soils. Specifically, it involves first applying a first module composition for physicochemical passivation, initially stabilizing heavy metals and adjusting pH; 7-10 days later, applying a second module composition for organic complexation and structural improvement, further passivating and improving soil physical structure; 3-5 days later, inoculating with microbial agents to rapidly colonize using the favorable environment created in the previous steps; and finally, planting hyperaccumulating plants for extraction and removal. This remediation method, through precise time-series control, solves the antagonistic problem in multi-component remediation, achieves synergistic effects, and provides long-lasting and stable remediation results, demonstrating significant environmental and economic benefits.

[0026] More specifically, compared with existing technologies, it has the following outstanding advantages:

[0027] 1. Disruptive Timing Design: Through precise timing control in four stages, the antagonistic problem between different functional components is completely solved, enabling each component to exert its maximum effectiveness in the optimal environment, achieving a synergistic effect of "1+1+1+1">4. Example results show that applying the first, second, and third module compositions in stages improves heavy metal passivation efficiency by more than 35% compared to a single application.

[0028] 2. Significantly improved remediation effect: The remediation method achieved removal rates of 82.5%, 76.8%, and 71.3% for available Cd, Pb, and As in the soil within 180 days, respectively, which are significantly better than the 47.2%, 41.5%, and 38.1% of the single-use mixed application method.

[0029] 3. Ecological benefits and long-term effectiveness: Through examples, it was found that the survival rate of the microorganisms was as high as 85% or more, and the rebound rate of the effective heavy metal content was less than 5% after 360 days. BCR continuous extraction speciation analysis showed that the proportion of residual state increased significantly, realizing the transformation from "temporarily fixed" to "long-term stable".

[0030] 4. Economic Efficiency and Applicability: The method has a clear logical structure, and the modular remediation components facilitate widespread adoption. Furthermore, the remediation components used in this invention can be used to remediate local agricultural waste and mineral resources, achieving a resource utilization rate exceeding 80%. The remediation cost is reduced to 450-550 yuan / ton, approximately 40% lower than traditional methods (700-800 yuan / ton). Detailed Implementation

[0031] The present invention also provides a composite conditioning module for the remediation of heavy metal pollution in acidic soil, comprising a first module composition, a second module composition, and a third module composition, each packaged separately. The total weight of the first module composition, the second module composition, and the third module composition is 100%, comprising 60% to 70% of the first module composition, 20% to 30% of the second module composition, and 8% to 10% of the third module composition.

[0032] The first module composition comprises 12%~20% modified tea biochar, 13%~20% modified straw biochar, 10%~15% calcium dihydrogen phosphate, and 15%~20% silicon-calcium-magnesium soil conditioner mineral powder;

[0033] The second module composition comprises 5%~10% anionic polyacrylamide, 3%~5% polyaspartic acid, 2%~4% polyglutamic acid, 2%~5% hydrolyzed polymaleic anhydride, and 8%~12% mineral-derived potassium humate;

[0034] The third module composition is a compound biological fertilizer, including Bacillus subtilis (Bacillus subtilis (B. subtilis)). Bacillus subtle ) and gelatinous spore-forming bacteria ( Paenibacillus mucilaginosus The effective live bacteria count of the compound biological fertilizer is ≥1 billion CFU / g.

[0035] As one implementation, based on the total amount of the composite conditioning module being 100%, the mass percentage of the first module composition is 65%. In the first module composition, as one implementation, the modified tea biochar has a tea polyphenol content ≥8.5% and a specific surface area ≥280m². 2 / g. As one embodiment, the preparation method of the modified tea biochar includes the following steps: pyrolyzing tea branches and / or tea residue at 290-310℃ under limited oxygen conditions of 5-10% for 1.5-3 hours to obtain the modified tea biochar. In this invention, the adsorption capacity of the modified tea biochar for Cd and Pb is ≥38mg / g and ≥85mg / g, respectively. As one embodiment, the tea branches and tea residue preferably use locally available resources; for example, when remediating heavy metal pollution in acidic soils of Guizhou, local tea tree waste resources are preferred. In this invention, the modified tea biochar has the effects of increasing soil pH, improving soil structure, and reducing the activity of heavy metal ions.

[0036] In one embodiment, the modified straw biochar of the present invention includes CO2-modified straw biochar. In another embodiment, the modified straw biochar has a fineness of 80-120 mesh, further 100 mesh; the modified biochar has a large specific surface area, abundant oxygen-containing functional groups, can loosen soil, and has strong chemical adsorption properties, showing significant improvement effects on acidic soils. In yet another embodiment, the preparation method of the modified straw biochar includes the following steps: pyrolyzing straw at a low-temperature (450-550℃) under a limited oxygen environment; after the pyrolysis is completed, introducing CO2 into the pyrolysis reaction vessel at 300-400℃ for surface activation modification; pulverizing the surface-activated modified material, sieving, and collecting the undersized fine powder to obtain the modified straw biochar. In one embodiment, the straw includes at least one of rice straw, wheat straw, and corn straw; the pulverization includes Raymond milling; the sieving uses a sieve with an aperture of 80-120 mesh, further 100 mesh; the CO2 flow rate is 0.5-1.5 L / min, and the CO2 introduction duration is 30-60 min. In traditional methods, biochar prepared by completely burning straw loses functional groups and specific surface area, resulting in very low value; biochar prepared by biological fermentation has a long fermentation time, uneven quality, and no commercial value. However, in this invention, after pyrolysis and CO2 modification, the specific surface area of ​​the straw biochar increases from the original 250-300 m² / g. 2 / g increased to 380~450m 2 / g, the surface carboxyl content increased from 0.7~0.9mmol / g to 1.3~1.5mmol / g.

[0037] In one embodiment, the silicon-calcium-magnesium soil conditioner mineral powder has a fineness ≥300 mesh, a CaO content ≥38%, a MgO content ≥8%, a SiO2 content ≥28%, and a pH of 9.5~11.0. In this invention, the silicon-calcium-magnesium soil conditioner mineral powder with the above properties has the effects of increasing soil pH, reducing the bioavailability of heavy metals, and improving soil structure.

[0038] As one implementation method, based on the total amount of the composite conditioning module being 100%, the mass percentage of the second module composition is 25%. In the second module composition, as one implementation method, the anionic polyacrylamide has a molecular weight of 12-15 million, exhibiting good flocculation properties, forming stable aggregate structures of soil particles, excellent fertilizer and water retention, and superior soil improvement effects; the polyaspartic acid has a molecular weight of 8000-12000, exhibiting strong water solubility, significant soil structure improvement, and a moderate molecular chain length, enabling efficient chelation of free heavy metal ions to form stable, insoluble chelates; the polyglutamic acid has a molecular weight of 10000-15000, exhibiting soil... The soil has high permeability, chelates free heavy metal ions to form insoluble chelates, and improves soil aggregate structure; the hydrolyzed polymaleic anhydride has a degree of hydrolysis ≥90%, which has the effect of efficiently chelating free heavy metal ions to form insoluble chelates and improving soil structure; the fulvic acid content in the mineral-derived potassium humate is ≥70%; the mineral-derived potassium humate is processed from lignite or weathered coal, rich in highly active functional groups, has good stability, can quickly neutralize acidic soil, reduce aluminum and manganese hazards, and significantly improve soil physical structure, chemical fertility and biological activity.

[0039] As one implementation method, based on the total amount of the composite conditioning module being 100%, the mass percentage of the third module composition is 10%. As another implementation method, the mass ratio of *Bacillus subtilis* and *Bacillus mucilaginosus* is 1:1. In this invention, *Bacillus subtilis* and *Bacillus mucilaginosus* are selected as composite biological agents. Their metabolites contain organic acids, polysaccharides, enzymes, and other substances, which can fix heavy metal ions through surface adsorption, ion exchange complexation, and other mechanisms, reducing their effectiveness. Furthermore, they can regulate the rhizosphere microenvironment, activate minerals such as calcium, silicon, and magnesium, and promote the stable precipitation of heavy metals.

[0040] This invention also provides the application of the composite conditioning module described above in the time-sequential remediation of heavy metal pollution in acidic soils. As one embodiment, the remediation of heavy metal pollution in acidic soils can involve the reconstruction of the acidic soil microbial community and / or the reduction of heavy metal content. As one embodiment, the pH value of the acidic soil is 4.5~6.0. As one embodiment, the heavy metals include, but are not limited to, one or more of Cd, Pb, and As. As one embodiment, the acidic soil can be acidic soil in karst landform areas, more specifically, acidic soil in karst landform areas of southern China, or acidic soil in southwestern China, such as acidic soils in Guangxi Zhuang Autonomous Region, Guizhou Province, or Yunnan Province.

[0041] This invention also provides a time-series precise remediation method for heavy metal pollution in acidic soils, utilizing the composite conditioning module described in the above technical solution for remediation, including a sequential physical and chemical passivation stage, a structural improvement and complexation stage, a biological activation stage, and a plant synergistic extraction stage, comprising the following steps:

[0042] The physical and chemical passivation stage includes: after applying the first module composition to the acidic soil contaminated with heavy metals, deep tilling of the acidic soil contaminated with heavy metals.

[0043] The structural improvement and complexation stage includes: 7 to 10 days after deep plowing, applying the second module composition to the acidic soil contaminated with heavy metals after deep plowing, and then rotary tilling.

[0044] The bioactivation stage includes: 3 to 5 days after rotary tillage, applying the third module composition to the acidic soil contaminated with heavy metals after rotary tillage, performing shallow tillage, and then irrigating to 60% to 70% of field capacity;

[0045] The plant synergistic extraction stage includes: planting hyperaccumulating plants 7-10 days after irrigation, and continuously planting for 3 growth cycles; the hyperaccumulating plants include the following percentages of plants: Sedum aizoon 40%-60%, Centipede grass 20%-30%, and Solanum nigrum 10%-20%.

[0046] In the physicochemical passivation stage, as one embodiment, the application amount of the first module composition is 2.5% to 3.5% of the mass of the acidic soil, more specifically 2.5% to 3.0%. As another embodiment, the deep tillage depth is 25 to 30 cm, or 26 to 28 cm. By applying the first module composition containing a pH adjuster, a chemical passivator, and an adsorbent to acidic soil contaminated with heavy metals, the pH value of the acidic soil can be adjusted to 6.2 to 6.8, promoting the formation of phosphate precipitates or fixation of heavy metals such as Cd, Pb, and As through ion exchange.

[0047] Furthermore, in the structural improvement and complexation stage, as one implementation method, the application rate of the second module composition is 1.0% to 1.5% of the acidic soil mass, or it can be 1.2% to 1.4%. As another implementation method, the rotary tillage depth is 15 to 20 cm, or it can be 16 to 18 cm. By applying the second module composition containing an organic complexing agent and a soil structure modifier, variable-valence heavy metals such as As and Hg can be complexed and fixed, and the soil aggregate structure can be improved simultaneously, creating a physical environment for microbial colonization.

[0048] Furthermore, in the bioactivation stage, as one implementation method, the application rate of the third module composition is 0.8% to 1.2% of the acidic soil mass, or 0.9% to 1.1%. As another implementation method, the shallow tillage depth is >0 cm and ≤10 cm. This invention, by applying the third module composition to acidic contaminated soil, enables microorganisms to rapidly colonize in an optimized chemical and physical environment, further stabilizing heavy metals and initiating ecological restoration through microbial action.

[0049] Finally, in the phytosynergistic extraction stage, as one implementation method, the ratio of the three hyperaccumulating plants—Sedum aizoon, Centipede Grass, and Black Nightshade—can be 3:2:1. In this invention, Sedum aizoon is a typical Zn / Cd hyperaccumulator, exhibiting extremely strong absorption capacity for Zn and Cd in acidic soils (above-ground Zn content can reach 10,000~30,000 mg / kg dry weight). It grows rapidly, has a large biomass, and is suitable for the remediation of large-scale contiguous polluted sites, while also showing good acid and barrenness tolerance. Centipede Grass is a representative As hyperaccumulator, possessing highly efficient enrichment capacity for different forms of As in acidic soils (above-ground As content can reach 1,000~5,000 mg / kg dry weight), and can also tolerate certain concentrations of Pb and Cd. Its well-developed root system allows it to adapt to the harsh structure of acidic soils, making it widely used in acid-contaminated mining areas. The described black nightshade is a broad-spectrum heavy metal accumulator, exhibiting good absorption effects on Cd, Pb, Cu, and other heavy metals in acidic soils. It is drought- and acid-tolerant, has strong reproductive capacity, is easy to cultivate and manage, and possesses a large biomass. Based on these advantages, as one implementation method, this invention selects three plants with large biomass and robust phenotypes for planting. As one implementation method, the planting density of the hyperaccumulator plants is 3000-4000 plants / acre. As one implementation method, in each of the three growth cycles, depending on the local climate, the hyperaccumulator plants are harvested when their biomass is at its maximum, which is 80-120 days into their growth. This invention utilizes the root system of hyperaccumulator plants to absorb partially activated heavy metals by planting a hyperaccumulator plant community. When the community's biomass is at its maximum, the above-ground parts are harvested to permanently remove the heavy metals from the soil.

[0050] In this invention, the application or planting time intervals of the four stages are designed to fully consider the time required for the previous module to take effect. The next module is carried out only after the previous module has fully taken effect, so that each module can play a stable role and lay the foundation for the next step of treatment. In this way, the modules work together to achieve the purpose of controlling heavy metals.

[0051] In one implementation, the remediation of heavy metal pollution in acidic soil can involve reconstructing the microbial community of the acidic soil and / or reducing the heavy metal content. In one implementation, the pH value of the acidic soil is 4.5–6.0. ​​In one implementation, the heavy metals include, but are not limited to, one or more of Cd, Pb, and As. In one implementation, the acidic soil can be acidic soil from karst landform areas, more specifically acidic soil from karst landform areas in southern China, or acidic soil from southwestern China, such as acidic soil from Guangxi Zhuang Autonomous Region, Guizhou Province, or Yunnan Province.

[0052] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0053] Example 1

[0054] A composite module for the remediation of heavy metal pollution in acidic soils consists of three independent modules, wherein the total weight of the first, second, and third modules is 100%, as detailed below:

[0055] The first module consists of the following components by weight percentage: 20% modified tea biochar, 15% modified straw biochar, 15% calcium dihydrogen phosphate, and 15% silicon-calcium-magnesium soil conditioner mineral powder;

[0056] The preparation steps of modified tea biochar are as follows: Local Guizhou tea branches and / or tea residue are pyrolyzed at 300±10℃ under nitrogen protection with limited oxygen for 2 hours to obtain modified tea biochar. The modified tea biochar has a tea polyphenol content ≥8.5% and a specific surface area ≥280m². 2 / g, with adsorption capacities for Cd and Pb ≥38mg / g and ≥85mg / g, respectively.

[0057] The preparation steps of modified straw biochar are as follows: Rice, wheat, or corn straw is pyrolyzed at a low temperature of 450-550℃ under an oxygen-limited environment. After pyrolysis, CO2 is introduced into the reactor at 300-400℃ at a flow rate controlled at 0.5-1.5 L / min for 30-60 min to carry out surface activation modification. After this modification, the specific surface area of ​​the biochar increases from 250-300 m² / g to 250-300 m² / g. 2 / g increased to 380~450m 2 / g, the surface carboxyl content increased from 0.7~0.9mmol / g to 1.3~1.5mmol / g. The obtained biochar was pulverized by Raymond mill and taken as 80~120 mesh fine biochar powder.

[0058] The silicon-calcium-magnesium soil conditioner mineral powder is processed from local Guizhou minerals, with a fineness ≥300 mesh, CaO content ≥38%, MgO content ≥8%, SiO2 content ≥28%, and pH value 9.5~11.0.

[0059] Calcium dihydrogen phosphate was purchased from Hebei Baipin Biotechnology Co., Ltd.

[0060] The second module consists of the following components by weight percentage: 8% anionic polyacrylamide (molecular weight 15 million), 5% polyaspartic acid (molecular weight 8000), 2% polyglutamic acid (molecular weight 15000), 2% hydrolyzed polymaleic anhydride (degree of hydrolysis ≥90%), and 8% mineral-derived potassium fulvic acid (fulvic acid content ≥70%).

[0061] Anionic polyacrylamide was produced by Shandong Aote Materials Co., Ltd.; hydrolyzed polymaleic anhydride was produced by Shandong Qifeng Chemical Co., Ltd.; polyaspartic acid and polyglutamic acid were produced by Shandong Taihe Technology Co., Ltd. and Shandong Jienuo Biotechnology Co., Ltd.; and mineral-derived potassium humate was produced by Xinjiang Shengda Yifang Biotechnology Co., Ltd., etc.

[0062] The third module is a compound bio-fertilizer with a weight ratio of 10% and an effective live bacteria count of ≥1 billion CFU / g.

[0063] The compound bio-fertilizer is composed of Bacillus subtilis and Bacillus mucilaginosus in a 1:1 weight ratio, with effective viable counts of 500 million CFU / g for Bacillus subtilis and 500 million CFU / g for Bacillus mucilaginosus.

[0064] Bacillus subtilis and Bacillus jellyoidis were produced by Shandong Baiwo Biotechnology Co., Ltd. and Anhui Guoren Biotechnology Co., Ltd., respectively.

[0065] Example 2

[0066] A time-sequential remediation method for acidic soil heavy metal pollution consists of the following four sequential stages:

[0067] The interval between the four phases is based on the time of application of the third module (T0) as the absolute reference, T0- Before the third module is applied, the sky indicates the time. My God, T0+ After the third module is applied, Tian indicates that... sky.

[0068] 1. Physical and chemical passivation stage (T0-12 days): Apply the first module composition, then deeply plow the soil to a depth of 25-30 cm to mix it evenly. The application amount is 2.5% of the soil mass.

[0069] 2. Structural improvement and complexation stage (T0-5 days): Apply the second module composition, then till the soil to a depth of 15-20 cm to mix it evenly. The application rate is 1.5% of the soil mass.

[0070] 3. Bioactivation stage (on day T0): Apply the third module composition, then lightly mix it with the soil at a depth of 0-10 cm, and immediately irrigate to 60%-70% of field capacity. The application rate is 1.2% of the soil mass.

[0071] 4. Plant Synergistic Extraction Stage (T0+9 days): Plant a hyperaccumulating plant community with 3500 plants per acre, consisting of the following percentages of hyperaccumulating plants: Sedum aizoon 50%, Centipede Grass 33.33%, and Black Nightshade 16.67% (Sedum aizoon: Centipede Grass: Black Nightshade ≈ 3:2:1). Perform three consecutive growth cycles, harvesting at the point of maximum biomass (80-120 days) according to local climate.

[0072] Example 3

[0073] Verification of the effectiveness of the time-series remediation method for heavy metal pollution in acidic soil in Example 2

[0074] Acidic heavy metal soils in the Wanshan mining area of ​​Guizhou Province were remediated. The initial soil conditions were: pH 5.1, Cd 3.8 mg / kg, Pb 850 mg / kg and As 145 mg / kg.

[0075] Experimental group: The repair method in Example 2 was strictly followed.

[0076] Control group 1: During T0-12 days, all components of the first, second and third modules of Example 1 were mixed and applied at once, with a total application amount of 5.2% of the soil mass. The hyperaccumulating plants were planted in the same way as the experimental group.

[0077] Control group 2: During T0-12 days, lime (CaO) was applied to adjust the pH to 6.5, with the total amount applied being 5.2% of the soil mass. The planting of hyperaccumulating plants was the same as in the experimental group.

[0078] 180 days after the application of the first module composition (control group 1 was given the mixed components, and control group was given lime), the contents of available Cd, available Pb and available As in the remediated soil were measured, and the removal rate was calculated. The results are shown in Table 1.

[0079] Table 1 Heavy metal content in acidic soil before and after remediation

[0080]

[0081] Table 1 shows that the acidic soil heavy metal pollution remediation method of the present invention is significantly superior to traditional one-time mixed application and lime treatment in terms of heavy metal passivation efficiency and ecological benefits.

[0082] 360 days after the application of the first module composition (control group 1 was given the mixed components, and control group was given lime), the pH of the soil after remediation in the experimental group remained stable at 6.5±0.2, and the content of available Cd rebounded slightly from 0.67 mg / kg to 0.70 mg / kg, with a rebound rate of 4.5%. In contrast, the content of available Cd in control group 1 rebounded from 2.01 mg / kg to 2.45 mg / kg, with a rebound rate of 21.9%. Heavy metal contamination assessment (BCR speciation analysis) of sediments showed that in the experimental group, the proportion of residual Cd increased from 15% to 68%, residual Pd from 20% to 75%, and residual As from 10% to 62%. In contrast, in control group 1, the proportion of residual Cd only increased from 15% to 35%, residual Pd from 20% to 42%, and residual As from 10% to 31%; in control group 2, the proportion of residual Cd only increased from 15% to 30%, residual Pd from 20% to 35%, and residual As from 10% to 28%. This demonstrates that the remediation method described in this invention exhibits good long-term stability.

[0083] Example 4

[0084] Soils with different levels of heavy metal pollution were selected and remediated using the sequential remediation method described in Example 2 of this invention. Specifically, after applying the first, second, and third modules according to the application process in Example 2, hyperaccumulating plants were planted. The soil pollution level, heavy metal content, conditioner dosage, heavy metal removal rate, and Cd accumulation in the plants are shown in Table 2. The conditioner dosage is the total amount applied in the first, second, and third modules, expressed as a percentage of soil mass. The application ratio of the first, second, and third modules was 2.5:1.5:1.2.

[0085] Table 2. Remediation status of acidic soils with heavy metal pollution using time-series remediation methods for soils with different pollution levels.

[0086]

[0087] Table 2 shows that the sequential remediation method for heavy metal pollution in acidic soil described in this invention has a good remediation effect on acidic soils with different levels of pollution.

[0088] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A time-series precise remediation method for heavy metal pollution in acidic soil, characterized in that, Repair is performed using a composite conditioning module, which includes independently packaged first module composition, second module composition, and third module composition. The total weight of the first module composition, second module composition, and third module composition is 100%, comprising 60%~70% of the first module composition, 20%~30% of the second module composition, and 8%~10% of the third module composition. The first module composition comprises 12%~20% modified tea biochar, 13%~20% modified straw biochar, 10%~15% calcium dihydrogen phosphate, and 15%~20% silicon-calcium-magnesium soil conditioner; The second module composition comprises 5%~10% anionic polyacrylamide, 3%~5% polyaspartic acid, 2%~4% polyglutamic acid, 2%~5% hydrolyzed polymaleic anhydride, and 8%~12% mineral-derived potassium humate; The third module composition is a compound biological fertilizer, including Bacillus subtilis (Bacillus subtilis (B. subtilis)). Bacillus subtilis ) and gelatinous spore-forming bacteria ( Paenibacillus mucilaginosus The effective live bacteria count of the compound biological fertilizer is ≥1 billion CFU / g; The time-series precise remediation method for heavy metal pollution in acidic soils includes a sequential physicochemical passivation stage, a structural modification and complexation stage, a biological activation stage, and a plant-assisted extraction stage, comprising the following steps: The physical and chemical passivation stage includes: after applying the first module composition to the acidic soil contaminated with heavy metals, deep tilling of the acidic soil contaminated with heavy metals. The structural improvement and complexation stage includes: 7 to 10 days after deep plowing, applying the second module composition to the acidic soil contaminated with heavy metals after deep plowing, and then rotary tilling. The bioactivation stage includes: 3 to 5 days after rotary tillage, applying the third module composition to the acidic soil contaminated with heavy metals after rotary tillage, performing shallow tillage, and then irrigating to 60% to 70% of field capacity; The plant synergistic extraction stage includes: planting hyperaccumulating plants 7-10 days after irrigation, and continuously planting for 3 growth cycles; the hyperaccumulating plants include the following percentages of plants: Sedum aizoon 40%-60%, Centipede grass 20%-30%, and Black nightshade 10%-20%; The pH value of the acidic soil is 4.5~6.

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2. The time-series precise remediation method for heavy metal pollution in acidic soil according to claim 1, characterized in that, The application rate of the first module composition is 2.5% to 3.5% of the mass of acidic soil; the application rate of the second module composition is 1.0% to 1.5% of the mass of acidic soil; the application rate of the third module composition is 0.8% to 1.2% of the mass of acidic soil; and the planting density of the hyperaccumulating plants is 3,000 to 4,000 plants per mu.

3. The time-series precise remediation method for heavy metal pollution in acidic soil according to claim 1, characterized in that, The depth of deep tillage is 25-30cm; the depth of rotary tillage is 15-20cm; and the depth of shallow tillage is >0cm and ≤10cm.

4. The time-series precise remediation method for heavy metal pollution in acidic soil according to any one of claims 1 to 3, characterized in that, The remediation of heavy metal pollution in acidic soils includes the reconstruction of acidic soil microbial communities and / or reduction of heavy metal content.

5. The time-series precise remediation method for heavy metal pollution in acidic soil according to any one of claims 1 to 3, characterized in that, The heavy metals include one or more of Cd, Pb, As, and Hg.

6. The time-series precise remediation method for heavy metal pollution in acidic soil according to claim 1, characterized in that, The modified tea biochar has a tea polyphenol content of ≥8.5% and a specific surface area of ​​≥280m². 2 / g; the modified straw biochar includes CO2 modified straw biochar; the silicon-calcium-magnesium soil conditioner mineral powder has a fineness ≥300 mesh, CaO content ≥38%, MgO content ≥8%, SiO2 content ≥28%, and pH 9.5~11.

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7. The time-series precise remediation method for heavy metal pollution in acidic soil according to claim 1, characterized in that, The anionic polyacrylamide has a molecular weight of 12-15 million, the polyaspartic acid has a molecular weight of 8,000-12,000, the polyglutamic acid has a molecular weight of 10,000-15,000, the hydrolysis degree of the hydrolyzed polymaleic anhydride is ≥90%, and the fulvic acid content in the mineral-derived potassium fulvicate is ≥70%.

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