Rice heavy metal adsorption and isolation method based on iron agent regulation and control
By forming an iron film in paddy soil, utilizing its high affinity and complexing ability, heavy metals are fixed, solving the problem of heavy metal accumulation in rice, enhancing rice tolerance and reducing food chain risks, and providing a solution for farmland soil remediation and safe crop production.
Patent Information
- Application Number
- CN202510906934.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-02
- Publication Date
- 2025-11-18
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Existing technologies fail to fully utilize the formation of iron films in the soil, thus failing to effectively adsorb and isolate heavy metals in rice, affecting rice growth and human health.
By applying a specific iron agent to paddy soil, an iron film is induced to form at the soil-rhizosphere interface, which is used to adsorb and complex heavy metals, thereby reducing their migration to rice roots.
It significantly reduces the accumulation of heavy metals in the edible parts of rice, enhances rice's tolerance to polluted environments, reduces the risk of heavy metals in the food chain, and provides solutions for farmland soil remediation and safe crop production.
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Figure CN120959089A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of agricultural pollution prevention technology, specifically relating to a method for adsorption and isolation of heavy metals in farmland crops. Background Technology
[0002] During rice cultivation, the accumulation of heavy metals, particularly arsenic (As), copper (Cu), lead (Pb), cadmium (Cd), and zinc (Zn), not only affects rice growth but may also impact human health through the food chain. While existing methods exist for treating heavy metal pollution, most fail to fully utilize natural processes, such as the formation of iron films in the soil, to reduce the absorption of heavy metals by rice. This invention aims to form an iron film in paddy field soil, utilizing the film's high affinity and complexing ability to effectively adsorb and isolate heavy metals in the soil, preventing them from entering rice plants and remediating the polluted soil environment. Summary of the Invention
[0003] This invention addresses the shortcomings of existing technologies by providing an iron-based method for the adsorption and isolation of heavy metals in rice, which can effectively prevent heavy metal pollution.
[0004] This invention applies a specific iron agent to contaminated paddy soil to induce the formation of an iron film at the soil-rhizosphere interface. The iron film is then used to adsorb and complex heavy metals (such as As, Cu, Pb, Cd, Zn, etc.) and reduce their migration to the rice roots. This reduces the accumulation of heavy metals in the edible parts of rice (leaves and panicles), enhances the rice's tolerance to polluted environments, and reduces the risk of heavy metals in the food chain.
[0005] The method for adsorption and isolation of heavy metals in rice based on iron-modified agents provided by this invention includes the following specific steps:
[0006] S1. Prepare materials: Prepare suitable rice seeds, initial culture solution for rice seedlings, iron agent and heavy metal solution;
[0007] S2. Rice seed pretreatment: Rice seeds are placed in a dark environment for germination treatment. After germination, the seedlings are transferred to the initial culture solution for initial culture to obtain rice seedlings.
[0008] S3. Inducing the formation of an iron film in rice roots through iron treatment: The specific operation of iron treatment is as follows: rice seedlings are transferred to different concentrations of Fe. 2+ In solution, Fe 2+ The pH of the solution was maintained at 5-5.5 for hydroponics of rice seedlings. During the cultivation process, the initial culture solution was continued to be used to cultivate the seedlings in order to induce the formation of an iron film in the roots.
[0009] S4. Heavy metal exposure: After the iron film is formed, the treated rice seedlings are transferred to a heavy metal nutrient solution.
[0010] S5. Sample collection and analysis of heavy metal adsorption in rice seedlings: During the period of heavy metal exposure, samples were collected from the nutrient solution and the changes in the concentration of heavy metal ions were analyzed.
[0011] S6. Evaluate the effect of iron film on heavy metal isolation: By measuring the specific content of heavy metals on the iron film, evaluate the isolation effect of the iron film in reducing the migration of heavy metals to the upper part of rice.
[0012] Furthermore:
[0013] In step S1, the initial culture medium is a 25% Hoagland nutrient solution, the iron agent is ferrous sulfate heptahydrate, i.e., FeSO4·7H2O; the heavy metal solution includes CuSO4·5H2O solution, Pb(NO3)2 solution, CdCl2·2.5H2O solution, ZnSO4·7H2O solution, NaAsO3 solution and NaAsO2 solution.
[0014] In step S2, the germination treatment lasts for one week at a temperature of 25-28°C to ensure that all seeds can germinate fully and are at similar developmental stages.
[0015] The initial culture was conducted at a constant temperature of 25°C; the light conditions consisted of 16 hours of light and 8 hours of darkness, with the relative humidity maintained between 60-70% to simulate the diurnal rhythm and humidity environment suitable for rice growth; the culture period was 2 weeks.
[0016] In step S3, before the iron treatment, the rice seedlings are soaked in deionized water for 12 hours to remove interference from other elements present on the root surface.
[0017] The Fe 2+ The solution concentration range was 4-20 mg / L, obtained through systematic experimental optimization and screening. Multiple Fe concentration gradients were set. 2+ Concentration comparison experiments were conducted, and the treatment efficiency was comprehensively evaluated by combining multiple indicators such as free radical generation, root adsorption capacity, and heavy metal isolation effect. Ultimately, this concentration range was determined to have good environmental responsiveness and repeatability. Fe was the preferred choice. 2+ The solution concentration range is 10-15 mg / L. Relevant data have been verified in the examples.
[0018] In step S4, the nutrient solution containing exposed heavy metals includes Cu. 2+ (e.g., 10 mg / L CuSO4·5H2O), Pb 2+ (e.g., 4 mg / L Pb(NO3)2), Cd 2+ (e.g., 0.3 mg / L CdCl2·2.5H2O), Zn2+ (e.g., 3 mg / L ZnSO4·7H2O), As 5+ (e.g., 4 mg / L NaAsO3) and As 3+ (4 mg / L NaAsO2).
[0019] After the treated rice seedlings are transferred to a heavy metal nutrient solution, they are sealed to reduce interference from external pollutants.
[0020] In step S5, the analysis of the concentration change of heavy metal ions specifically involves: after the heavy metal exposure is completed, the roots, stems and leaves of rice are separated; for the root part, the iron film is extracted using the DCB extraction method to determine the content of heavy metals adsorbed on it; then, the roots, stems and leaves are digested using a mixed acid of HNO3-H2O, and finally the specific content of heavy metals in each part is determined to assess the adsorption and accumulation of heavy metals in each part.
[0021] In step S6, the evaluation of the iron film's effect on heavy metal isolation specifically involves: after completing the heavy metal analysis of root and leaf samples, calculating the adsorption capacity of the iron film by measuring the specific content of heavy metals on the iron film, comparing the differences in heavy metal content in the roots and leaves, and evaluating the isolation effect of the iron film in reducing the migration of heavy metals to the aboveground parts of rice.
[0022] The principle of heavy metal adsorption and isolation based on iron film is as follows:
[0023] (1) Formation of the iron film: The iron film is a precipitate layer of iron hydroxide formed on the surface of rice roots through a redox reaction. Under the conditions of oxygen secretion in the rhizosphere, Fe... 2+ Oxidized to Fe 3+ This process deposits an iron film on the root surface. The surface of this iron film contains abundant active sites, which can adsorb heavy metal ions from the environment through chemical bonding.
[0024] (2) Selective adsorption of heavy metals: The structure of FeOOH in the iron film provides multiple complexation and adsorption sites for heavy metals. As 3+ Pb 2+ and Cu 2+ Due to their high charge density, metals such as FeOOH can form stable chemical bonds with the FeOOH surface; while Cd... 2+ The adsorption is achieved through weak electrostatic attraction. This process effectively reduces the mobility of these heavy metal ions.
[0025] The generated iron film forms a dual physical and chemical barrier on the root surface, limiting the migration of heavy metals to the above-ground parts of the plant, especially by preventing them from entering the stems and leaves from the roots, thereby reducing the accumulation of heavy metals in the leaves.
[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0027] By forming an iron film on the surface of rice roots, the high affinity and complexing ability of the iron film effectively immobilize heavy metals (such as As, Cu, Pb, Cd, and Zn) on the root surface, thereby significantly reducing the transfer of heavy metals to leaves and other edible parts, enhancing the plant's tolerance to polluted environments, and reducing the risk of heavy metals in the food chain. Promoting the formation of the iron film on rice roots enables selective adsorption and isolation of various heavy metals, effectively reducing the migration of heavy metals from polluted environments to the aboveground parts of rice. The formation of the iron film not only acts as a physical barrier to prevent the translocation of heavy metals but also immobilizes them on the root surface through chemical adsorption, improving the survival ability of rice in heavy metal-polluted environments. Treatment with an iron film at a certain iron concentration significantly reduced the accumulation of heavy metals (such as As, Cu, Pb, Cd, and Zn) in rice leaves. Experiments showed that the accumulation of heavy metals in rice leaves was far lower than that in rice roots (1 / 40–1 / 120). This invention provides an effective solution for farmland soil remediation and safe crop production. Attached Figure Description
[0028] Figure 1 This is a schematic diagram illustrating the adsorption and removal of different metals (As, Cd, Cu, Pb) in paddy soil under the action of an iron film.
[0029] Figure 2 This is a schematic diagram illustrating the adsorption and removal of various metals by iron films formed in rice at different iron concentrations according to the present invention.
[0030] Figure 3 This is a schematic diagram illustrating the cumulative amount of metals (Cu, Zn, As, Cd, Pb) in roots and leaves under different Fe concentrations according to the present invention.
[0031] Figure 4 The rice hydroponic system of this invention is Fe 2+ Fe extracted from the DCB film formed by treating the iron film without heavy metals and with heavy metals. Detailed Implementation
[0032] The present invention will be further described below with reference to the embodiments and accompanying drawings.
[0033] Example: A method for heavy metal adsorption and isolation in paddy fields based on iron-modified control, with experimental process and environmental simulation of paddy field rice cultivation scenario.
[0034] S1. Prepare materials:
[0035] Rice seeds from the Guangdong Academy of Agricultural Sciences Rice Research Institute were used in the experiment to ensure its reliability and practicality. A quarter-concentration Hoagland nutrient solution was used as the initial culture medium for rice seedlings to provide the basic nutrients required for plant growth. In addition, to induce the formation of iron film in the roots, an Fe2+ solution was prepared. 2+ The solutions used ferrous sulfate heptahydrate (FeSO4·7H2O) as the iron source, with concentrations set at 4 mg / L, 10 mg / L, and 20 mg / L. Simultaneously, various heavy metal solutions, including Cu, were also prepared. 2+ (10 mg / L CuSO4·5H2O), Pb 2+ (4 mg / L Pb(NO3)2), Cd 2+ (0.3 mg / L dCl2·2.5H2O), Zn 2+ (3mg / L ZnSO4·7H2O), As 5+ (4 mg / L NaAsO3) and As 3+ (4 mg / L NaAsO2); These concentrations are based on preliminary experimental results from polluted paddy fields in Guixi, with the aim of simulating metal concentrations in actual polluted environments.
[0036] S2. Rice seed pretreatment:
[0037] At the start of the experiment, the rice seeds underwent pretreatment to ensure healthy seedling growth in subsequent experiments. First, the rice seeds were placed in a dark environment for one week to promote germination. During this period, the temperature was maintained at around 25℃, and the humidity was suitable to ensure that all seeds germinated fully and were at similar developmental stages. In this process, the dark environment inhibited unnecessary photosynthesis, concentrating resources on root and shoot growth.
[0038] After germination, the seedlings were transferred to 96-well plates containing one-quarter concentration of Hoagland nutrient solution for initial cultivation. The cultivation stage was conducted at a constant temperature of 25°C, with a light cycle of 16 hours light and 8 hours dark, and a relative humidity of 60-70% to simulate the suitable diurnal rhythm and humidity environment for rice growth. This cultivation stage lasted for two weeks to ensure the seedlings developed sufficiently robust root and leaf systems to adapt to subsequent iron-film induction and heavy metal treatment experiments.
[0039] S3. Inducing the formation of an iron film in rice roots through iron source treatment:
[0040] In the experiment, iron source treatment was first used to induce iron film formation in rice roots. Specifically, 21-day-old rice seedlings were soaked in deionized water for 12 hours to remove any other elements that might interfere with the root surface, thus ensuring that the influence of iron film formation came solely from the external iron source. During the iron source treatment stage, the seedlings were transferred to different concentrations of Fe. 2+ In solutions (concentrations set at 4 mg / L, 10 mg / L, and 20 mg / L Fe) 2+ The solution, derived from ferrous sulfate heptahydrate (FeSO4·7H2O), was maintained at a pH of 5.5. Rice seedlings were hydroponically cultured in 500mL blue-necked flasks, with three seedlings per flask. During the cultivation process, the seedlings were continuously cultured with a quarter-concentration of Hoagland nutrient solution for four days to induce the formation of an iron film on the roots.
[0041] To detect and characterize the formation of the iron film, the DCB (sodium disulfide-citric acid-sodium carbonate) extraction method was used to determine the thickness and coverage of the iron film, ensuring successful formation and adhesion of the iron film to the root surface. Furthermore, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) was used to characterize the morphology and elemental distribution of the iron film, further confirming its structure and adsorption potential for heavy metals.
[0042] S4. Heavy metal exposure:
[0043] After the iron film was formed, the treated rice seedlings were transferred to a nutrient solution containing heavy metals to simulate a multi-metal contamination environment. The heavy metal solution used included Cu. 2+ (10 mg / L CuSO4.5H2O), Pb 2+ (4 mg / L Pb(NO3)2), Cd 2+ (0.3 mg / L CdCl2·2.5H2O), Zn 2+ (3 mg / L ZnSO4.7H2O) and As 3+ (4 mg / L NaAsO2). Each blue-necked bottle contained 250 mL of heavy metal nutrient solution, with two seedlings placed in each bottle. The bottle openings were sealed again with wax to reduce interference from external contaminants. To ensure the stability of the heavy metal concentration during the experiment, the heavy metal nutrient solution was changed every 3 days during the 14-day exposure period.
[0044] S5. Sample Collection and Analysis: Adsorption of heavy metals by rice seedlings:
[0045] During heavy metal exposure, to monitor the dynamic changes in heavy metal concentrations, samples were initially collected from the nutrient solution every 2 hours, and subsequent intervals were used to analyze the changes in heavy metal ion concentrations. Inductively coupled plasma mass spectrometry (ICP-MS) was used to ensure the accuracy of the results. After the exposure experiment, the roots, stems, and leaves of rice were separated. For the roots, the iron film was first extracted using DCB extraction to determine the content of heavy metals adsorbed on it. Then, the roots and leaves were digested using a mixed acid of HNO3-H2O-HCl, and the specific content of heavy metals in each part was finally determined to assess the adsorption and accumulation of heavy metals in each component.
[0046] S6. Evaluate the effectiveness of the iron film in isolating heavy metals:
[0047] After completing the heavy metal analysis of root and leaf samples, the adsorption capacity of the iron film for As, Cd, Cu, Pb, and Zn was calculated by determining the specific heavy metal content on the iron film, expressed in mg / g iron film. Simultaneously, by comparing the differences in heavy metal content between roots and leaves, the isolation effect of the iron film in reducing the migration of heavy metals to the aboveground parts of rice was further evaluated.
[0048] The ability to fix lead is somewhat affected, leading to a weakening of its lead-fixing effect. This indicates its significant importance for phytoremediation of heavy metal pollution and for agricultural production safety.
[0049] Experimental Results and Analysis
[0050] Fe 2+ The effect of concentration on the adsorption and fixation of heavy metals such as As, Cd, and Pb
[0051] Experimental results show that arsenic (As) in different Fe... 2+ All concentrations (4-20 mg / L) were rapidly removed from the solution within 5 hours, with the 10 mg / L and 20 mg / L treatment groups showing more significant reductions, reaching near-zero residual concentrations. The 4 mg / L group had slightly higher residual concentrations, indicating that Fe... 2+ Increasing the concentration significantly accelerates the adsorption and fixation rate of arsenic. Similarly, the initial concentration of Pb was 2.5 mg / L, which rapidly decreased to near zero in all treatments within 2 hours, with the 10 mg / L and 20 mg / L treatments showing better results; while a small amount of residue remained in the 4 mg / L treatment group, indicating that high concentrations of Fe... 2+ This is more conducive to the rapid fixation of Pb. The initial Cu concentration was 2.5 mg / L, which decreased to about 1.5 mg / L within 5 hours and remained stable, indicating that its adsorption mainly occurred in the initial stage, and Fe... 2+ Concentration had little effect on it. Cd concentration increased slightly at the beginning of the treatment, then stabilized after 40 hours, and Fe... 2+The higher the concentration, the lower the final concentration of Cd in the solution, indicating that the iron film formation also has the ability to adsorb Cd, but the adsorption rate is slower than that of As and Pb.
[0052] Different Fe 2+ The effect of concentration on the accumulation of heavy metals in rice tissues;
[0053] Rice roots in different Fe 2+ Significant differences were observed in the accumulation of heavy metals at different concentrations. Taking Cu as an example, at 4 mg / L Fe... 2+ The highest Cu concentration (approximately 6000 mg / kg) was observed in the roots of the treatment group, while Fe concentration was lower. 2+ When the concentration was increased to 20 mg / L, the root accumulation decreased, indicating that high concentrations of Fe... 2+ The entry of Cu may be limited by the formation of a dense iron film. Zn at 10 mg / L Fe 2+ The highest root accumulation was observed in the 10 mg / L treatment group (approximately 800 mg / kg), while it was slightly lower in the 4 mg / L and 20 mg / L groups, suggesting the existence of an optimal adsorption window. As accumulation in the roots was also highest in the 10 mg / L treatment group (approximately 5000 mg / kg), indicating that the iron film formed at this concentration had the strongest adsorption and fixation capacity for As. Cd showed a similar trend, with the highest Cd concentration in the roots in the 10 mg / L treatment group and the lowest in the 20 mg / L group, presumably due to the high concentration of Fe. 2+ Excessive precipitation may have inhibited adsorption efficiency. Pb content was extremely low in leaves across all treatments, while the highest adsorption capacity was observed in the root system at 4 mg / L. Fe... 2+ Increasing the concentration actually reduces the adsorption capacity.
[0054] Optimal Fe 2+ Summary and conclusion of concentration ranges;
[0055] A comprehensive analysis of the above dynamic changes and tissue accumulation data leads to the clear conclusion that: Fe 2+ The concentration range of 10 mg / L exhibits the best adsorption and isolation effects, with strong removal capabilities for heavy metals such as As, Cd, and Pb, and the largest root accumulation, effectively inhibiting their migration to the aboveground parts. At too low a concentration (e.g., 4 mg / L), insufficient iron film formation results in limited adsorption capacity; while at too high a concentration (20 mg / L), excessive iron film deposition and densification, along with reduction inhibition, may reduce adsorption efficiency.
[0056] Therefore, the preferred Fe of the present invention 2+ The treatment concentration range is 4–20 mg / L, with 10–15 mg / L being particularly preferred. Under these conditions, a structurally stable and highly absorbent iron film layer can be formed on the root surface, thus achieving the most significant effect in phytoremediation and pollution isolation. Relevant performance data can be used to support the claim regarding "optimal Fe".2+ The range of "treatment concentration".
[0057] Different Fe 2+ Comparison of iron film formation (DCB-Fe) under different concentration treatments;
[0058] To further evaluate different Fe 2+ The effect of concentration on the formation of iron film on the root surface of rice was investigated by extracting and quantifying the iron film on the root surface using the DCB (Dithionite-Citrate-Bicarbonate) method. The results are as follows: Figure 4 As shown.
[0059] Under conditions without heavy metal stress (IP), as Fe... 2+ As the concentration increased from low Fe (4 mg / L) to moderate Fe and high Fe (20 mg / L), the amount of iron film extracted by DCB increased significantly, to approximately 1.8, 3.1, and 3.3 g / kg, respectively, indicating that higher Fe concentrations resulted in a higher iron film content. 2+ Concentration can promote the deposition of more iron films.
[0060] Under heavy metal coexistence conditions (IP+HMs), the overall DCB-Fe level was slightly lower than that of the heavy metal-free group. This is presumably because heavy metal stress interfered with root oxygen secretion activity or iron reduction / precipitation behavior, consuming some DCB-Fe. However, it still exhibited Fe... 2+ The concentration-dependent increase was observed, with the DCB-Fe in the high-Fe group reaching approximately 3.0 g / kg, significantly higher than that in the low-Fe group (approximately 1.6 g / kg).
[0061] The above results further verify that in Fe 2+ Within a concentration range of 10 mg / L, it can effectively induce the formation of a stable and extractable iron film structure in the rice rhizosphere, providing a physical basis for the adsorption and isolation of heavy metals, and also for the Fe proposed in the claims. 2+ The optimal treatment concentration range provides direct data support.
[0062] This invention provides a method for heavy metal adsorption and isolation based on an iron film, applicable to safe crop production in environments with multi-metal complex pollution. By generating an iron film on the surface of rice roots, the high affinity and complexing ability of the iron film are effectively utilized to fix heavy metals (such as As, Cu, Pb, Cd, and Zn) on the root surface, thereby significantly reducing the transfer of heavy metals to leaves and other edible parts, enhancing the plant's tolerance to polluted environments, and reducing the risk of heavy metals in the food chain. By promoting the formation of the iron film on rice roots, selective adsorption and isolation of multiple heavy metals are achieved, effectively reducing the migration of heavy metals from polluted environments to the aboveground parts of rice. The formation of the iron film not only acts as a physical barrier to prevent the translocation of heavy metals, but also fixes heavy metals to the root surface through chemical adsorption, improving the survival ability of rice in heavy metal polluted environments. Iron film treatment significantly reduces the accumulation of heavy metals (such as As, Cu, Pb, Cd, and Zn) in rice leaves, thus providing an effective solution for farmland soil remediation and safe crop production.
[0063] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.
Claims
1. A method for adsorption and isolation of heavy metals in rice based on iron-modified agents, characterized in that, By applying iron to contaminated paddy soil, an iron film is induced to form at the soil-rhizosphere interface. This film, through adsorption and complexation, immobilizes heavy metals, reducing their migration to the rice roots. This decreases the accumulation of heavy metals in the edible parts of the rice, enhances the rice's tolerance to polluted environments, and reduces the risk of heavy metal contamination in the food chain. The heavy metals are As, Cu, Pb, Cd, and Zn. The specific steps are as follows: S1. Prepare materials: Prepare suitable rice seeds, as the initial culture solution for rice seedlings, iron agent and heavy metal solution; S2. Rice seed pretreatment: Rice seeds are placed in a dark environment for germination treatment. After germination, the seedlings are transferred to the initial culture solution for initial culture to obtain rice seedlings. S3. Inducing the formation of an iron film in rice roots through iron treatment: The specific operation of iron treatment is as follows: rice seedlings are transferred to different concentrations of Fe. 2+ In solution, Fe 2+ The pH of the solution was maintained at 5-5.5 for hydroponics of rice seedlings. During the cultivation process, the initial culture solution was continued to be used to cultivate the seedlings in order to induce the formation of an iron film in the roots. S4. Heavy metal exposure: After the iron film is formed, the treated rice seedlings are transferred to a heavy metal nutrient solution. S5. Sample collection and analysis of heavy metal adsorption in rice seedlings: During the period of heavy metal exposure, samples were collected from the nutrient solution and the changes in the concentration of heavy metal ions were analyzed. S6. Evaluate the effect of iron film on heavy metal isolation: By measuring the specific content of heavy metals on the iron film, evaluate the isolation effect of the iron film in reducing the migration of heavy metals to the upper part of rice.
2. The method according to claim 1, characterized in that, In step S1, the initial culture medium is a 25% Hoagland nutrient solution, the iron agent is ferrous sulfate heptahydrate, and the heavy metal solution is CuSO4·5H2O solution, Pb(NO3)2 solution, CdCl2·2.5H2O solution, ZnSO4·7H2O solution, NaAsO3 solution, and NaAsO2 solution.
3. The method according to claim 2, characterized in that, In step S2, the germination treatment lasts for one week at a temperature of 25-28°C to ensure that all seeds can germinate fully and are at similar developmental stages. The initial culture was conducted at a constant temperature of 25°C; the light conditions consisted of 16 hours of light and 8 hours of darkness, with the relative humidity maintained between 60-70% to simulate the diurnal rhythm and humidity environment suitable for rice growth; the culture period was 2 weeks.
4. The method according to claim 3, characterized in that, In step S3, before the iron treatment, the rice seedlings are soaked in deionized water for 12 hours to remove interference from other elements present on the root surface. The Fe 2+ The concentration of the solution is 4-20 mg / L.
5. The method according to claim 4, characterized in that, In step S4, the nutrient solution exposed to heavy metals consists of 10 mg / L CuSO4·5H2O, 4 mg / L Pb(NO3)2, 0.3 mg / L CdCl2·2.5H2O, 4 mg / L NaAsO3, and 4 mg / L NaAsO2. The treated rice seedlings are transferred to the heavy metal nutrient solution and sealed to reduce interference from external pollutants.
6. The method according to claim 5, characterized in that, In step S5, the analysis of the concentration change of heavy metal ions specifically involves: after the heavy metal exposure is completed, the roots, stems and leaves of rice are separated; for the root part, the iron film is extracted using the DCB extraction method to determine the content of heavy metals adsorbed on it; then, the roots, stems and leaves are digested using a mixed acid of HNO3-H2O, and finally the specific content of heavy metals in each part is determined to assess the adsorption and accumulation of heavy metals in each part.
7. The method according to claim 6, characterized in that, In step S6, the evaluation of the iron film's effect on heavy metal isolation specifically involves: after completing the heavy metal analysis of root and leaf samples, calculating the adsorption capacity of the iron film by measuring the specific content of heavy metals on the iron film, comparing the differences in heavy metal content in the roots and leaves, and evaluating the isolation effect of the iron film in reducing the migration of heavy metals to the aboveground parts of rice.