Ecological restoration method for regulating and fixing heavy metals by utilizing rhizosphere effect

Abstract

The invention discloses an ecological restoration method for regulating and fixing heavy metals by utilizing a rhizosphere effect, and belongs to the technical field of water environment ecological restoration. According to the method, the pollution degree, form and release risk of target heavy metal in the sediment are determined through pollution diagnosis, then submerged plants with specific rhizosphere oxygen secreting and acidification capacity are screened in a targeted mode for single planting or mixed planting, a stable submerged plant community is constructed, iron and manganese oxides are formed through induction of the plant rhizosphere effect, and the target heavy metal in the sediment is obtained. According to the method, the in-situ remediation of heavy metal pollution is realized, the function of rhizosphere microflora is regulated and controlled, the form of the heavy metal with higher activity is converted into a stable form or is adsorbed and fixed on a rhizosphere iron membrane, meanwhile, the remediation process can be monitored through an in-situ high-resolution monitoring technology, and finally, the in-situ remediation of the heavy metal pollution and the collaborative restoration of a water ecosystem are realized. The method is clear in mechanism, high in pertinence, environment-friendly, low in cost and monitorable in effect, and can be widely applied to remediation of sediment heavy metal pollution of shallow water bodies such as lakes, river channels and ponds.

Description

Technical Field

[0001] This invention relates to the field of aquatic environment ecological restoration technology, specifically to an ecological restoration method that utilizes the rhizosphere effect of submerged plants to regulate and fix heavy metals in sediments, thereby reducing their bioavailability and mobility, and more specifically to an ecological restoration method that utilizes the rhizosphere effect to regulate and fix heavy metals. Background Technology

[0002] Lake sediments are important sinks for heavy metals in water bodies, but under changing environmental conditions, they can transform into sources of heavy metals, causing secondary pollution to overlying water bodies. Currently, sediment heavy metal remediation technologies mainly include physical dredging, chemical passivation, and bioremediation. Physical and chemical methods are costly, easily disrupt the sediment ecosystem, and may cause secondary pollution. Bioremediation, especially phytoremediation, has gained attention due to its advantages such as low cost, environmental friendliness, and sustainability.

[0003] Submerged plants, as an important component of aquatic ecosystems, create a unique rhizosphere microenvironment through their root activities (such as oxygen secretion, acidification, and organic matter secretion), which can significantly alter the physical, chemical, and biological properties of sediments, thereby affecting the occurrence, migration, transformation, and bioavailability of heavy metals. Current technologies for remediating heavy metal pollution using submerged plants largely focus on the direct absorption and accumulation of heavy metals by plants, while neglecting the "in-situ fixation" and "activity regulation" mechanisms of plant rhizosphere effects on heavy metals in sediments. The remediation mechanisms remain unclear, and the selection of remediation plants lacks specificity, leading to unstable remediation efficiency and uncertain effects.

[0004] Existing technologies include methods for remediating heavy metal-polluted water bodies using submerged plants, but these methods mainly rely on the overall absorption capacity of the plants and do not fully consider or utilize the differentiated regulatory capacity of different submerged plants on the migration of specific heavy metals through rhizosphere effects. Therefore, their applicability to remediation scenarios aimed at reducing the activity of heavy metals rather than completely removing them is limited.

[0005] Therefore, there is an urgent need for an ecological restoration method based on the rhizosphere effect mechanism of submerged plants, which can specifically regulate and fix different types of heavy metals in sediments and inhibit their release into the overlying water. Summary of the Invention

[0006] In view of this, the purpose of this invention is to overcome the shortcomings of the prior art and provide an ecological restoration method based on the rhizosphere effect mechanism of submerged plants, which can efficiently and directionally regulate and fix heavy metals in sediments.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] An ecological restoration method utilizing rhizosphere effects to regulate and immobilize heavy metals includes the following steps:

[0009] S1. Pollution diagnosis and remediation target identification: Samples are taken from the surface and columnar sediments of the water area to be remediated. The total amount, chemical form and sediment-water interface diffusion flux of the target heavy metals are analyzed to assess the pollution level, potential bioavailability and release risk of the heavy metals and identify the target heavy metal species.

[0010] S2. Screening and combination configuration of remediation plants: Based on the diagnostic results of step S1, select submerged plant species or combinations with corresponding strong rhizosphere effects;

[0011] S3. Planting and Community Construction: In the water area to be restored, plant planting methods are selected based on water transparency, water depth and bottom conditions, and the selected submerged plants are planted at the designed density.

[0012] S4. Rhizosphere microenvironment enhancement and process monitoring: In-situ high-resolution monitoring technology was used to dynamically monitor the two-dimensional spatial distribution of dissolved oxygen, pH and available heavy metals in the rhizosphere of submerged plants.

[0013] S5. Restoration effect assessment and long-term maintenance: After one or more growth cycles, assess the restoration effect. Once the expected restoration effect is achieved, carry out routine aquatic ecosystem maintenance.

[0014] Preferably, the target heavy metal in step S1 includes at least one of Cr, Ni, Cu, Zn, As, Cd, Hg, and Pb; the chemical speciation analysis is performed using the BCR continuous extraction method or the Tessier method; and the sediment-water interface diffusion flux is determined using the thin film diffusion gradient technique (DGT).

[0015] Preferably, the classification of heavy metal pollution levels in step S1 is as follows:

[0016] Potential ecological risk coefficient of a single metal ( The potential ecological risk index (PRI) is the core indicator for evaluating the ecological risk of a single heavy metal in the potential ecological risk index method. The coefficient is the benchmark.

[0017] clean: ;

[0018] Mild: ;

[0019] Moderate: ;

[0020] Severe: .

[0021] The potential bioavailability of heavy metals was determined using BCR / Tessier speciation analysis, which included the proportion of highly active forms, exchangeable forms, and carbonate-bound forms (also known as weakly acid-soluble forms, B1). Exchangeable forms (F1) are non-specifically adsorbed (weakly adsorbed, most readily released), while carbonate-bound forms (F2) are weakly acid-sensitive co-precipitates / bound components (released upon pH decrease). The sum of these two forms is F1 + F2. Highly active form = weakly acid-soluble form = exchangeable form + carbonate-bound form, i.e., B1 = F1 + F2. When B1 > 30%, the heavy metal is considered to have potential bioavailability.

[0022] The risk of heavy metal release is calculated using DGT diffusion flux. A value above the critical value is considered high risk. The critical value is usually the diffusion flux of the control area and is greater than 0.

[0023] The specific criteria for determining the types of targeted heavy metals are: pollution + potential bioavailability + release risk. If two or more of these three criteria indicate a high risk, then a highly targeted heavy metal can be identified.

[0024] Preferably, the submerged plants mentioned in step S2 include one or more of Vallisneria natans, Potamogeton crispus, Hydrilla verticillata, and Potamogeton malaianus. The specific method for plant selection and combination configuration is as follows:

[0025] For areas where the water transparency is less than 50 cm, choose Hydrilla verticillata or Potamogeton malaianus;

[0026] For areas with water transparency greater than 50 cm, Vallisneria natans is selected for areas polluted by As and Cd, while Potamogeton crispus is selected for areas polluted by Pb or areas where nutrient removal and landscape effects need to be considered simultaneously.

[0027] Preferably, the different plant cultivation methods described in step S3 are as follows:

[0028] For water bodies with a transparency ≥1.0 m, propagation can be carried out by sowing or cuttings.

[0029] The water transparency is 0.5-1.0 m, and seedlings are transplanted.

[0030] If the water transparency is less than 0.5 m, the turbidity can be quickly reduced by means of ecological flocculation sedimentation, local ecological dredging or emergency algae removal. First, improve the water quality and increase the transparency to ensure that the underwater light environment reaches the minimum survival threshold of submerged plants and meets the photosynthetic needs of submerged plants. Then, seedlings can be transplanted.

[0031] For water depths ≤ 1.5 m, propagation can be done by sowing or cuttings.

[0032] The water depth is 1.5-3.0 m. Seedlings are propagated by cuttings or transplanting, and an enclosure is set up.

[0033] For water depths greater than 3.0 m, it is not recommended or is necessary to select species with extremely strong resistance to deep water (such as *Vallisneria natans*, *Ceratophyllum demersum*, *Hydrilla verticillata*, *Potamogeton pectinatus*, etc.) and use engineering fixation. Deep water bodies face core challenges such as strong wind and wave disturbances, water erosion, and poor root anchorage. Therefore, bottom anchoring engineering (fixing rooted submerged plants, such as *Vallisneria natans*, *Potamogeton pectinatus*, etc.) and plant suspension engineering (fixing rootless submerged plants, such as *Ceratophyllum demersum*, *Hydrilla verticillata*, etc.) can be used in conjunction with wave-damping engineering to further improve the survival rate of submerged plants.

[0034] The substrate conditions are loam or silty soil, and propagation is carried out by sowing or cutting.

[0035] The substrate conditions are sandy soil or hard soil. Seedlings are transplanted and the substrate is improved. Sandy soil has problems such as poor water and fertilizer retention and easy root lodging. Physical or biological methods can be used to improve the water and fertilizer retention, fertilization and structural stability of the substrate. Hard soil has problems such as extremely high hardness (submerged plant seedlings cannot take root), poor water and fertilizer retention and extreme infertility. Physical or biological methods can be used to lay an artificial bedding layer on the hard soil to ensure the rooting conditions of submerged plants. At the same time, the fertility of the bedding layer can also promote the root development of seedlings and enhance the bedding layer's resistance to wind and waves.

[0036] When the substrate is contaminated or compacted, seedling transplantation is used, and the substrate is improved. When the substrate pollution is heavy metal contamination, the core of the improvement is to passivate the toxicity of heavy metals. This can be achieved through physical improvement (artificially laying a bedding layer to isolate the heavy metal-contaminated substrate), chemical improvement (adding heavy metal passivating agents to passivate the bioavailability of heavy metals and reduce their bioavailability), and biological improvement (adding biological agents to passivate heavy metals using microorganisms while promoting the root growth of submerged plants). When the substrate pollution is nutrient contamination, the core of the improvement is to reduce nitrogen and phosphorus release and break up organic compaction. This can be achieved through physical improvement (rotary tillage of the surface substrate to break up organic compaction), chemical improvement (adding passivating agents to adsorb active phosphorus in the substrate), and biological improvement (adding compound biological agents to degrade organic matter).

[0037] Preferably, in step S3, the designed density is 15-20 Vallisneria natans plants / m². 2 10-15 plants / m² of Potamogeton crispus 2 Other plants should be planted at a density of 10-20 plants / m². 2 .

[0038] Preferably, in step S4, the in-situ high-resolution monitoring technology includes planar optical poles and thin-film diffusion gradient technology.

[0039] Preferably, in step S5, the growth cycle is 1 year; the evaluation indicators for remediation effect include the proportion of effective heavy metals in the sediment, the diffusion flux at the sediment-water interface, and changes in the macrobenthic community structure.

[0040] Specifically, the effective proportion of the target heavy metal is less than 30%; the sediment-water interface diffusion flux changes from "positive" before remediation to "negative" after remediation, or if both before and after remediation are "positive", the flux decreases by 30% after remediation compared to before remediation; the indicator for macrobenthic community structure is the Shannon-Wiener diversity index (H), with a threshold generally of 3 (according to the standard of "Technical Guidelines for Water Ecological Monitoring: Monitoring and Evaluation of Aquatic Organisms in Lakes and Reservoirs (Trial) HJ1296-2023", H>3 is considered excellent), or the level is improved.

[0041] The principle of this invention lies in the fact that submerged plants secrete oxygen through their roots, creating an oxidation microzone in the rhizosphere, which promotes the growth of Fe in the root periphery sediment. 2+ Mn 2+ The iron oxides are oxidized to iron-manganese oxides / hydroxides and coat the root surface as "rust spots," forming a rhizosphere iron film. This iron film is resistant to arsenates and heavy metal cations (such as Cd). 2+ Pb 2+ Cu 2+ (etc.) exhibit strong specific adsorption and co-precipitation effects. Simultaneously, rhizosphere acidification (caused by root secretion of H+) also occurs. + Oxygen secretion (or caused by organic acids) can dissolve some iron and manganese oxides, releasing the heavy metals they adsorb. However, stronger oxygen secretion drives these metal ions to be re-oxidized and fixed on the root surface. Furthermore, the unique physicochemical environment of the rhizosphere screens and enriches specific functional microorganisms (such as iron-oxidizing bacteria and sulfur-oxidizing bacteria). The activities of these microorganisms further promote the formation of iron and manganese oxides and the transformation of heavy metal forms. This invention selects plants with different rhizosphere oxygen secretion / acidification capabilities to specifically enhance the "adsorption-fixation" pathway for specific heavy metals (such as As and Cd, which are easily fixed by iron films). Simultaneously, it converts active heavy metals into more stable bound states through rhizosphere processes, thereby reducing the activity and release risk of heavy metals from the "source," rather than simply relying on plant absorption.

[0042] As can be seen from the above technical solution, compared with the prior art, the present invention discloses an ecological restoration method that utilizes rhizosphere effects to regulate and fix heavy metals, which has the following beneficial effects:

[0043] (1) Highly targeted and with a clear mechanism: Based on the diagnosis of the heavy metal morphology and release risk in sediments, submerged plants with rhizosphere effects are selected to drive the formation of iron film and microbial processes through their rhizosphere oxidation / acidification, thereby targeting and fixing the heavy metals, and the remediation mechanism is clear.

[0044] (2) In-situ fixation, environmentally friendly: This method does not damage the sediment structure, does not introduce external chemical agents, and achieves the stabilization of heavy metals by enhancing natural ecological processes, thus avoiding secondary pollution and ecological damage.

[0045] (3) Dual benefits and synergistic restoration: The selected submerged plants can not only fix heavy metals, but also absorb nutrients such as nitrogen and phosphorus in the water, inhibit algae growth, improve water transparency, promote the restoration of a healthy aquatic ecosystem, and achieve synergy between heavy metal pollution control and water ecological restoration.

[0046] (4) The effect is monitorable and the process is controllable: It can be combined with high-resolution in-situ monitoring technologies such as PO and DGT to intuitively and dynamically evaluate the changes in the rhizosphere microenvironment and the effect of heavy metal fixation, making the remediation process visible, controllable and optimizable.

[0047] (5) Low cost and easy to promote: It mainly relies on the growth and metabolism of the plant itself, with low maintenance cost, simple technology, and easy to promote and apply on a large scale in shallow water bodies such as lakes, rivers, and ponds. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0049] Figure 1 Root structure diagrams for different submerged plants;

[0050] Figure 2 Iron spots on the surface of the roots of different submerged plants;

[0051] Figure 3 This is a two-dimensional distribution map of O2 concentration in the rhizosphere of Vallisneria natans, monitored using PO technology in the example.

[0052] Figure 4 The spatial and temporal variation of O2 concentration in the rhizosphere of *Potamogeton crispus* with root growth. Detailed Implementation

[0053] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0054] Example 1

[0055] Taking the remediation of Cd-contaminated sediments in Zhushan Bay, Taihu Lake as an example

[0056] S1. Pollution Diagnosis: Sediment surveys in the Zhushan Bay area of ​​Taihu Lake revealed that Cd was predominantly in highly reactive exchangeable and carbonate-bound forms (average percentage 47.46%). DGT measurements showed high interfacial diffusion flux of Cd in this area, with release fluxes ranging from 1.95 to 72.6 ng·cm³. -2 d -1 The average value was 20.48 ng·cm³. -2 d -1 There is a risk of release into the overlying water; the remediation goal is to reduce the bioavailable Cd content in the sediment and inhibit its release into the overlying water.

[0057] S2. Plant selection: Vallisneria natans exhibited the strongest root oxygen secretion capacity and rhizosphere iron film formation capacity, significantly reducing the flux of bioavailable As and Cd in the rhizosphere. Therefore, Vallisneria natans was selected as the core remediation plant in this embodiment.

[0058] S3. Planting and Construction: In the selected area of ​​Zhushan Bay, when the water temperature is stable above 15℃ in spring (April-May), plant 18 plants / m². 2 Plant Vallisneria seedlings at a density of approximately 10-15cm in height using cuttings. Set up soft fencing around the planting area to reduce the impact of wind and waves. Regularly observe the survival and growth of the plants.

[0059] S4. Process Monitoring: 45 days after planting, combined PO and DGT probes were deployed at typical locations. Monitoring showed that a significant O2 concentration gradient formed around the roots of Vallisneria natans (see...). Figure 3 A brown iron film appeared on the root surface. DGT monitoring showed that the Cd release flux gradually decreased, with an average value of 18±2 ng·cm⁻¹ around the rhizosphere. -2 d -1 In the region, the diffusion flux of non-rhizosphere Cd remains at 21±4 ng·cm⁻¹. -2 d -1 This confirmed the effectiveness of rhizosphere fixation.

[0060] S5. Effect Evaluation: After two growing seasons (approximately 24 months), sediment samples were collected from the remediation area and the control area (unplanted). Analysis showed that the proportion of acid-extractable (B1) Cd in the sediment of the remediation area decreased from an average of 47.5% to 28.3%. Simultaneously, based on the Cd diffusion flux at the sediment-water interface measured by DGT, the average Cd release flux in the remediation area was 7.42 ± 4 ng·cm³. -2 d -1The prevalence of pollution-tolerant groups (such as Hop's tubifex worms) decreased by 63.77%. Benthic animal surveys showed that the dominance of pollution-tolerant groups (such as Hop's tubifex worms) in the restoration area decreased, the biodiversity index increased, and the Shannon-Wiener diversity index increased from 1.21 before restoration to 3.04.

[0061] Comparative Example 1

[0062] In the same area as in Example 1, only *Hydrillaverticillata*, a species with relatively weak rhizosphere oxygen release capacity, was planted. After the same remediation time, the percentage of bioavailable Cd in the sediment did not decrease significantly (from 47.5% to 40.1%). DGT flux monitoring showed that the average Cd release flux was 16.42 ± 4 ng·cm³. -2 d -1 The reduction was only 20%. This indicates that, for Cd pollution, choosing Vallisneria natans, which has a strong rhizosphere oxygen-secreting capacity, has a significantly better remediation effect than choosing Hydrilla verticillata.

[0063] Experimental Example

[0064] Figure 1 The diagram shows the root system structure of different submerged plants. Figure 1 It can be seen that plants with different root structures have different rhizosphere oxygen secretion / acidification capabilities;

[0065] Figure 2 Iron spots on the surface of the roots of different submerged plants, by Figure 2 It can be seen that the formation of the rhizosphere iron film indicates that it can passivate or change the form of heavy metals, thereby reducing the toxicity of heavy metals.

[0066] Figure 4 The spatial and temporal variation of O2 concentration in the rhizosphere of *Potamogeton crispus* with root growth is given by... Figure 4 It can be seen that the spatiotemporal variation of rhizosphere O2 concentration can be compared with the spatiotemporal variation of rhizosphere iron film.

[0067] In summary, this invention, through a systematic approach of diagnosis, screening, planting, monitoring, and evaluation, fully utilizes the strong rhizosphere oxygen secretion and iron film formation capabilities of submerged plants (especially Vallisneria natans) to successfully fix highly active Cd in sediments in the rhizosphere, transforming it into a more stable form and effectively inhibiting its release into the overlying water. This achieves in-situ, green, and efficient ecological restoration of specific heavy metal pollution.

[0068] The embodiments described in this specification are presented in a progressive manner. The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An ecological restoration method utilizing rhizosphere effects to regulate and immobilize heavy metals, characterized in that, Includes the following steps: S1. Pollution diagnosis and remediation target identification: Samples are taken from the surface and columnar sediments of the water area to be remediated. The total amount, chemical form and sediment-water interface diffusion flux of the target heavy metals are analyzed to assess the pollution level, potential bioavailability and release risk of the heavy metals and identify the target heavy metal species. S2. Screening and combination configuration of remediation plants: Based on the diagnostic results of step S1, select submerged plant species or combinations with corresponding strong rhizosphere effects; S3. Planting and Community Construction: In the water area to be restored, plant planting methods are selected based on water transparency, water depth and bottom conditions, and the selected submerged plants are planted at the designed density. S4. Rhizosphere microenvironment enhancement and process monitoring: In-situ high-resolution monitoring technology was used to dynamically monitor the two-dimensional spatial distribution of dissolved oxygen, pH and available heavy metals in the rhizosphere of submerged plants. S5. Restoration effect assessment and long-term maintenance: After one or more growth cycles, assess the restoration effect. Once the expected restoration effect is achieved, carry out routine aquatic ecosystem maintenance.

2. The ecological restoration method for regulating and immobilizing heavy metals using rhizosphere effects according to claim 1, characterized in that, The target heavy metal mentioned in step S1 includes at least one of Cr, Ni, Cu, Zn, As, Cd, Hg, and Pb; chemical speciation analysis is performed using the BCR continuous extraction method or the Tessier method; and the diffusion flux at the sediment-water interface is determined using thin-film diffusion gradient technology.

3. The ecological restoration method for regulating and immobilizing heavy metals using rhizosphere effects according to claim 1, characterized in that, The classification of heavy metal pollution levels in step S1 is as follows: Based on the potential ecological risk coefficient of a single metal Based on, clean: ; Mild: ; Moderate: ; Severe: The potential bioavailability of heavy metals was determined using BCR / Tessier speciation analysis, which included the proportion of highly active forms, exchangeable forms, and carbonate-bound forms, also known as weakly acid-soluble forms, such as B1. The exchangeable state F1 is a non-specific adsorption state, and the carbonate-bound state F2 is a weak acid-sensitive coprecipitation / bound component. The sum of the two is F1 + F2. The highly active state = weak acid-soluble state = exchangeable state + carbonate-bound state, that is, B1 = F1 + F2. When B1 > 30%, the heavy metal is considered to have potential bioavailability. The risk of heavy metal release is calculated using DGT diffusion flux. A value higher than the threshold value is considered high risk. The threshold value is the diffusion flux of the control area, and the value is greater than 0. The specific criteria for determining the types of targeted heavy metals are: pollution + potential bioavailability + release risk; when two or more of the three criteria are considered high risk, a high-target heavy metal can be identified.

4. The ecological restoration method for regulating and immobilizing heavy metals using rhizosphere effects according to claim 1, characterized in that, The submerged plants mentioned in step S2 include one or more of Vallisneria natans, Potamogeton crispus, Hydrilla verticillata, and Potamogeton malaianus. The specific method for plant selection and combination configuration is as follows: For areas where the water transparency is less than 50 cm, choose Hydrilla verticillata or Potamogeton malaianus; For areas with water transparency greater than 50 cm, Vallisneria natans is selected for areas polluted by As and Cd, while Potamogeton crispus is selected for areas polluted by Pb or areas where nutrient removal and landscape effects need to be considered simultaneously.

5. The ecological restoration method for regulating and immobilizing heavy metals using rhizosphere effects according to claim 1, characterized in that, The different plant cultivation methods described in step S3 are as follows: For water bodies with a transparency ≥1.0 m, propagation can be carried out by sowing or cuttings. The water transparency is 0.5-1.0 m, and seedlings are transplanted. If the water transparency is less than 0.5 m, we will first use ecological flocculation sedimentation, local ecological dredging or emergency algae removal to quickly reduce turbidity and improve transparency, so as to ensure that the underwater light environment reaches the minimum survival threshold of submerged plants and meet their photosynthetic needs. Then, we will transplant seedlings. For water depths ≤ 1.5 m, propagation can be done by sowing or cuttings. The water depth is 1.5-3.0 m. Seedlings are propagated by cuttings or transplanting, and an enclosure is set up. For water depths greater than 3.0 m, it is not recommended or necessary to select species with extremely strong resistance to deep water, such as Elodea spicata, Ceratophyllum demersum, Hydrilla verticillata, and Potamogeton microdentatum, plus engineering fixation. The substrate conditions are loam or silty soil, and propagation is carried out by sowing or cutting. The substrate conditions are sandy soil or hard soil. Seedlings are transplanted and the substrate is improved. The substrate conditions were contaminated or compacted soil. Seedlings were transplanted and the substrate was improved.

6. The ecological restoration method for regulating and immobilizing heavy metals using rhizosphere effects according to claim 1, characterized in that, In step S3, the designed density is 15-20 Vallisneria natans plants / m². 2 10-15 plants / m² of Potamogeton crispus 2 Other plants should be planted at a density of 10-20 plants / m². 2 .

7. The ecological restoration method for regulating and immobilizing heavy metals using rhizosphere effects according to claim 1, characterized in that, In step S4, the in-situ high-resolution monitoring technology includes planar optical poles and thin-film diffusion gradient technology.

8. The ecological restoration method for regulating and immobilizing heavy metals using rhizosphere effects according to claim 1, characterized in that, In step S5, the growth cycle is 1 year; the evaluation indicators for remediation effect include the proportion of the target heavy metal in the sediment, the diffusion flux at the sediment-water interface, and changes in the macrobenthic community structure.

9. The ecological restoration method for regulating and immobilizing heavy metals using rhizosphere effects according to claim 8, characterized in that, The effective proportion of the target heavy metal is less than 30%; the sediment-water interface diffusion flux changes from "positive" before remediation to "negative" after remediation, or if both before and after remediation are "positive", the amount of flux decreases by 30% after remediation compared to before remediation; the indicator of macrobenthic community structure is an improvement in the Shannon-Wiener diversity index H level.

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