A combined remediation method for soil heavy metal pollution treatment and rice lodging resistance

Abstract

The present invention provides a combined remediation method for soil heavy metal pollution control and rice lodging resistance, comprising the following steps: (1) Select an acidified heavy metal pollution remediation area, and find the soil for safe utilization of heavy metal contaminated farmland according to the pH value and heavy metal content of the soil; (2) Sow in early September of the first year, use 2.5 - 3 Kg of seeds per mu of seedling land, evenly broadcast the seeds of Prunella vulgaris, and remove weeds regularly; (3) Thin the seedlings when the seedling height is 3 cm - 5 cm, remove the weak seedlings and keep the strong seedlings, and transplant when the seedlings grow to five leaves and one heart, and the transplanting ends at the end of October; (4) Harvest the medicinal parts of Prunella vulgaris with low heavy metal enrichment, namely the stalks, leaves and flowers, in May of the following year; (5) Harrow the soil and remove the roots of Prunella vulgaris with high heavy metal enrichment; (6) Apply the prepared soil acidification reduction and heavy metal conditioner 15 - 30 days before rice planting in the following year. The present invention can solve the problems of soil acidification heavy metal pollution and lodging at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of remediation of acidified heavy metal contaminated soil, and particularly to a combined remediation method for soil heavy metal pollution control and rice lodging resistance. Background Art

[0002] Soil acidification often leads to a decline in soil fertility. Some essential plant nutrients, such as phosphorus (P) and molybdenum (Mo), seem to be less soluble and available at low soil pH, which is related to the lack of calcium (Ca) and magnesium (Mg) in plant growth. Soil acidification also increases the solubility and mobility of metals in the soil, making them easily absorbed by plants. The characteristics of rice itself and its planting pattern cause rice to easily absorb and accumulate heavy metals in the environment, which poses a great threat to the quality and safety of rice. Paddy soil is an important carrier for rice growth. After heavy metals in the contaminated soil are accumulated and absorbed by rice, they enter the human body through the food chain. Since the biological half-life of heavy metals is very long, they can bind to organic macromolecules in the body, affecting the normal metabolic level of the human body. Therefore, studying the immobilization method of heavy metal ions in contaminated soil, solving the problem of soil acidification, and improving the safety quality of rice have very important theoretical and practical significance.

[0003] Currently, there are mainly two methods for the remediation of heavy metal contaminated soil. One is to remove the amount of soil contaminated by metals and replace it with uncontaminated soil, but this method is both expensive and destructive to the soil ecosystem and is not suitable for large-scale farmland soil remediation. The other method is to reduce the activity of metals and use in-situ stabilization technology to convert the form of heavy metals into a form that is difficult to dissolve and migrate or has less toxicity, thereby reducing its risk to the farmland ecosystem. In-situ stabilization technology is becoming more and more popular due to its advantages such as low cost and easy implementation. Therefore, more and more researchers are committed to developing various passivators. In the past few decades, some soil amendments, such as calcareous minerals limestone, oyster shell waste, etc., have been widely used in acidic contaminated cultivated land to increase soil pH and reduce the concentration of bioavailable heavy metals. However, one consideration for pure alkaline amendments is that over-application will lead to soil compaction and soil structure degradation. And the long-term effect is difficult to predict. Soil re-acidification easily leads to the reactivation of passivated heavy metals. Soil is an extremely complex changing environment, and there is also a risk of heavy metal activation only using in-situ passivation technology.

[0004] In addition, in rice production, lodging is also a common problem, seriously affecting the yield and quality of rice.

[0005] Currently, no technology can solve both the problems of soil acidification and heavy metal pollution and the problem of lodging at the same time. Therefore, how to solve the above problems and improve the yield and quality of rice is an urgent problem to be solved. Summary of the Invention

[0006] In view of the above situation, the present invention provides a combined remediation method for soil heavy metal pollution and rice lodging resistance, so as to repair acidified heavy metal polluted soil, improve the physical and chemical properties and structure of the soil, while reducing the rice lodging rate and improving the rice yield and quality.

[0007] The present invention provides a combined remediation method for soil heavy metal pollution and rice lodging resistance, comprising the following steps:

[0008] (1) Select an acidified heavy metal pollution remediation area, and find the soil for safe utilization of heavy metal polluted farmland according to the pH value and heavy metal content of the soil;

[0009] (2) Sow in early September of the first year, use 2.5 - 3 Kg of seeds per mu of seedling raising land, evenly broadcast the seeds of Prunella vulgaris, and remove weeds regularly;

[0010] (3) Thin the seedlings when the seedling height is 3 cm - 5 cm, remove the weak seedlings and keep the strong seedlings, and transplant when the seedlings grow to five leaves and one heart, and the transplanting ends at the end of October;

[0011] (4) Harvest the medicinal parts of Prunella vulgaris with low heavy metal enrichment, namely the stems, leaves and flowers, in May of the following year;

[0012] (5) Harrow the soil and remove the roots of Prunella vulgaris with high heavy metal enrichment;

[0013] (6) 15 - 30 days before the rice planting in the following year, apply the prepared soil acidification reduction and heavy metal conditioner, and the soil acidification reduction and heavy metal conditioner is composed of Xiuyu stone powder, activator and alkali co - solvent.

[0014] For the above - mentioned combined remediation method for soil heavy metal pollution and rice lodging resistance, the soil acidification reduction and heavy metal conditioner is prepared through the following steps:

[0015] S61, break the massive Xiuyu waste, crush it with a high - speed universal grinder and pass through a 100 - mesh sieve to obtain pretreated Xiuyu stone powder;

[0016] S62, weigh the pretreated Xiuyu stone powder, activator and alkali co - solvent according to the ratio and mix them evenly;

[0017] S63, calcine the evenly - mixed materials in a muffle furnace, cool them after calcination, and grind them to 200 meshes with a ball mill to obtain the soil acidification reduction and heavy metal conditioner;

[0018] S64, directly use the obtained soil acidification reduction and heavy metal conditioner as a powder product, or prepare it into a granular product by means of disk granulation, extrusion molding or hot - press molding.

[0019] In the above-mentioned soil heavy metal pollution control and rice lodging resistance combined restoration method, the weight percentage of Xiuyan jade powder in the soil acidification and heavy metal reduction conditioner is 60% to 70%, the weight percentage of the activator is 15% to 32%, and the weight percentage of the alkali co-solvent is 8% to 15%.

[0020] In the above-mentioned soil heavy metal pollution control and rice lodging resistance combined restoration method, the activator is a mixture of potassium carbonate and calcium carbonate and the ratio of the two is (1-1.4):1,

[0021] In the above-mentioned soil heavy metal pollution control and rice lodging resistance combined restoration method, the alkaline co-solvent is one or more of sodium hydroxide and potassium hydroxide.

[0022] In the above-mentioned soil heavy metal pollution control and rice lodging resistance combined restoration method, wherein, in step (6), the application amount of the soil acidification and heavy metal reduction conditioner is 200-300 kg / mu.

[0023] In the above-mentioned soil heavy metal pollution control and rice lodging resistance combined restoration method, step (3) is specifically as follows:

[0024] Thinning out the seedlings begins when they are 3cm-5cm tall, removing the weak seedlings and keeping the strong ones. The seedlings can be transplanted when they have five leaves and one bud. Transplanting is completed at the end of October, with a plant spacing of 25cm×30cm.

[0025] In the above-mentioned soil heavy metal pollution control and rice lodging resistance combined restoration method, in step S63, the conditions for muffle furnace calcination are: 600-700° C. continuous calcination for 1.5-3.5 hours.

[0026] Beneficial effects:

[0027] (1) The present invention discloses a method for controlling soil heavy metal pollution and restoring rice lodging resistance. The method realizes Prunella vulgaris-rice dry-water rotation by planting Prunella vulgaris and restoring the soil with a soil acidifier and heavy metal reducer. Dry-water rotation can improve soil physical and chemical properties, solve the problem that long-term application of passivators easily leads to soil structure degradation, and can also reduce pests and diseases and improve crop yield and quality.

[0028] (2) The root secretions of Prunella vulgaris inhibit the absorption of heavy metals and improve the physical and chemical properties of soil such as pH. Heavy metals in the soil can be removed by removing the roots of Prunella vulgaris.

[0029] (3) Among them, the soil acidification reduction and heavy metal conditioner contains Xiuyu stone powder. There are unsaturated Si-O-Si, O-Si-O bonds and magnesium bonds on the fracture surface of Xiuyu stone, which have high chemical activity. They can interact with heavy metals through adsorption, chelation and other effects, and their alkalinity can also solve the problem of soil acidification. In addition, Xiuyu stone is a silicate mineral containing a large amount of silicon. After activation, it can be absorbed by rice, enhancing the lodging resistance of rice. It integrates the functions of soil acidification reduction, heavy metal treatment and rice lodging resistance.

[0030] (4) The raw material of Xiuyu stone can be low-quality Xiuyu stone and its processing waste. It has low cost, does not contain harmful heavy metals or other harmful substances, is conducive to resource recovery and utilization, turning waste into treasure, is environmentally friendly, and has good economic benefits.

[0031] (5) The preparation process of the present invention is simple, highly operable, saves manpower and material resources, and is easy to promote on a large scale.

[0032] (6) The present invention integrates the functions of soil acidification reduction, heavy metal treatment and rice lodging resistance. Combined with the combined remediation of Prunella vulgaris - rice dry-wet rotation, it solves the problems of high cost of treating heavy metal pollution in acidified soil and serious lodging of rice, and has no secondary pollution and good economic benefits. Brief Description of the Drawings

[0033] Figure 1 It is a schematic flow chart of the combined remediation method for soil heavy metal pollution control and rice lodging resistance;

[0034] Figure 2 It is a graph of cadmium content in different parts of Prunella vulgaris planted in heavy metal-polluted farmland during the flowering period in Example 1 of the present invention;

[0035] Figure 3 It is a graph of the effect of planting Prunella vulgaris on soil cadmium content in Example 1 of the present invention;

[0036] Figure 4 It is the SEM image of the soil acidification reduction and heavy metal conditioner before (a) and after (b) adsorbing heavy metal cadmium, lead and copper complex pollution;

[0037] Figure 5 It is the FT-IR graph (a) and XRD graph (b) of the soil acidification reduction and heavy metal conditioner before and after adsorbing heavy metals. Detailed Embodiments

[0038] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to each embodiment. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0040] Please refer to Figure 1 , an embodiment of the present invention provides a combined remediation method for soil heavy metal pollution and rice lodging resistance, comprising the following steps:

[0041] (1) According to the screening values of soil pollution risks for agricultural land in the "Soil Environmental Quality Standards" (GB15618 - 2018), select the acidified heavy metal pollution remediation area, and then find the soil for safe utilization of heavy metal - polluted farmland according to the pH value and heavy metal content of the soil;

[0042] (2) Sow in early September of the first year, use 2.5 - 3 Kg of seeds per mu of the seedling - raising land, evenly broadcast the seeds of Prunella vulgaris, and regularly remove weeds;

[0043] (3) Start thinning when the seedling height is 3 cm - 5 cm, remove weak seedlings and keep strong seedlings. When the seedlings grow to five leaves and one heart, they can be transplanted, and the transplantation ends at the end of October;

[0044] (4) In May of the following year, harvest the medicinal parts of Prunella vulgaris with low heavy metal enrichment, namely the stems, leaves, and flowers;

[0045] (5) Harrow the soil to remove the roots of Prunella vulgaris with high heavy metal enrichment;

[0046] (6) 15 - 30 days before the rice planting in the following year, apply the prepared soil acidification and heavy metal reduction conditioner, which is composed of Xiuyu stone powder, activator, and alkali co - solvent.

[0047] For the above - mentioned combined remediation method for soil heavy metal pollution and rice lodging resistance, the soil acidification and heavy metal reduction conditioner is prepared through the following steps:

[0048] S61, Break the massive Xiuyu waste into pieces, crush it with a high - speed universal pulverizer and pass through a 100 - mesh sieve to obtain the pretreated Xiuyu stone powder;

[0049] S62, Weigh the pretreated Xiuyu stone powder, activator, and alkali co - solvent according to the ratio and mix them evenly;

[0050] S63, Calcinate the evenly - mixed materials in a muffle furnace. After calcination, cool them and grind them to 200 - mesh with a ball mill to obtain the soil acidification and heavy metal reduction conditioner;

[0051] S64, using the obtained soil acid regulating and heavy metal reducing conditioner directly as a powder product, or preparing it into a granular product by disc granulation, extrusion molding, or hot pressing molding.

[0052] In the above-mentioned soil heavy metal pollution control and rice lodging resistance combined restoration method, the weight percentage of Xiuyan jade powder in the soil acidification and heavy metal reduction conditioner is 60% to 70%, the weight percentage of the activator is 15% to 32%, and the weight percentage of the alkali co-solvent is 8% to 15%.

[0053] In the above-mentioned soil heavy metal pollution control and rice lodging resistance combined restoration method, the activator is a mixture of potassium carbonate and calcium carbonate and the ratio of the two is (1-1.4):1,

[0054] In the above-mentioned soil heavy metal pollution control and rice lodging resistance combined restoration method, the alkaline co-solvent is one or more of sodium hydroxide and potassium hydroxide.

[0055] In the above-mentioned soil heavy metal pollution control and rice lodging resistance combined restoration method, wherein, in step (6), the application amount of the soil acidification and heavy metal reduction conditioner is 200-300 kg / mu.

[0056] In the above-mentioned soil heavy metal pollution control and rice lodging resistance combined restoration method, step (3) is specifically as follows:

[0057] Thinning out the seedlings begins when they are 3cm-5cm tall, removing the weak seedlings and keeping the strong ones. The seedlings can be transplanted when they have five leaves and one bud. Transplanting is completed at the end of October, with a plant spacing of 25cm×30cm.

[0058] In the above-mentioned soil heavy metal pollution control and rice lodging resistance combined restoration method, in step S63, the conditions for muffle furnace calcination are: 600-700° C. continuous calcination for 1.5-3.5 hours.

[0059] The following is a further description of the embodiments of the present invention in multiple embodiments. The embodiments of the present invention are not limited to the following specific embodiments. Within the scope of the unchanged main rights, appropriate changes can be made to the implementation.

[0060] Embodiment 1:

[0061] A method for controlling soil heavy metal pollution and preventing rice from lodging, comprising the following steps:

[0062] (1) A heavy metal contaminated farmland area in Jiangxi Province was selected, with a soil pH of 5.50 and a total cadmium content of 1.13 mg / kg. The cadmium content of the soil in this area was higher than the agricultural land soil pollution risk screening value of the Soil Environmental Quality Standard (GB15618-2018);

[0063] (2) In the first year, sow in early September, use 2.5 kg of seeds per mu of nursery land, evenly sow Prunella vulgaris seeds, and remove weeds regularly;

[0064] (3) Thinning begins when the seedlings are 3-5 cm tall, removing weak seedlings and keeping strong ones. When the seedlings have five leaves and one heart, they can be transplanted. Transplanting is completed by the end of October, with a plant spacing of 25 cm × 30 cm.

[0065] (4) In May of the following year, the medicinal parts of Prunella vulgaris, such as stems, leaves, and flowers, which have low heavy metal accumulation, were harvested;

[0066] (5) harrowing the soil to remove the roots of Prunella vulgaris that are highly enriched with heavy metals;

[0067] (6) 30 days before rice planting in the following year, apply the prepared soil acidification and heavy metal reduction conditioner. The application amount of the soil acidification and heavy metal reduction conditioner is 300 kg / mu. The soil acidification and heavy metal reduction conditioner is composed of Xiuyan jade powder, an activator, and an alkali cosolvent.

[0068] Wherein, the soil acidification and heavy metal reduction conditioning agent is prepared by the following steps:

[0069] S61, breaking up the blocky Xiuyu waste, crushing it with a high-speed universal grinder and passing it through a 100-mesh sieve to obtain pretreated Xiuyu stone powder;

[0070] S62, weighing the pretreated Xiuyu stone powder, activator, and alkaline solvent according to a ratio and mixing them evenly, wherein the weight percentage of Xiuyu stone powder is 60%, the weight percentage of activator is 32%, and the weight percentage of alkaline solvent is 8%, the activator is a mixture of potassium carbonate and calcium carbonate in a ratio of 1:1, and the alkaline solvent is sodium hydroxide;

[0071] S63, the uniformly mixed material is calcined in a muffle furnace, the calcination condition is: calcination at 600° C. for 2 hours, cooling after calcination, and ball milling to 200 meshes using a ball mill to obtain a soil acidification and heavy metal reduction conditioning agent;

[0072] S64, the obtained soil acid-regulating and heavy metal-reducing conditioner is directly used as a powder product, or is prepared into a granular product by disc granulation, extrusion molding, or hot pressing molding. In this embodiment, the obtained soil acid-regulating and heavy metal-reducing conditioner is directly used as a powder product.

[0073] Embodiment 2:

[0074] A method for controlling soil heavy metal pollution and preventing rice from lodging, comprising the following steps:

[0075] (1) Select a farmland area with safe utilization of heavy metal pollution in Jiangxi. The soil pH value is 5.25, and the total cadmium content in the soil is 1.21 mg / Kg. The cadmium content in the soil of this area is higher than the risk screening value of agricultural land soil pollution in the "Soil Environmental Quality Standards" (GB15618-2018);

[0076] (2) Sow in early September of the first year. Use 3 Kg of seeds per mu of seedling land, evenly spread the seeds of Prunella vulgaris, and remove weeds regularly;

[0077] (3) When the seedling height is 3 cm - 5 cm, start thinning the seedlings, remove the weak seedlings and keep the strong seedlings. When the seedlings grow to five leaves and one heart, they can be transplanted. The transplanting ends at the end of October, and the plant spacing is 25 cm × 30 cm;

[0078] (4) In May of the following year, harvest the medicinal parts of Prunella vulgaris with low heavy metal enrichment, namely the stalks, leaves and flowers;

[0079] (5) Harrow the soil and remove the roots of Prunella vulgaris with high heavy metal enrichment;

[0080] (6) 15 days before planting rice in the following year, apply the prepared soil acidification and heavy metal reduction conditioner. The application amount of the soil acidification and heavy metal reduction conditioner is 200 Kg / mu. The soil acidification and heavy metal reduction conditioner is composed of Xiuyu stone powder, activator and alkali co-solvent.

[0081] Among them, the soil acidification and heavy metal reduction conditioner is prepared through the following steps:

[0082] S61, crush the massive Xiuyu waste, pulverize it with a high-speed universal pulverizer and pass through a 100-mesh sieve to obtain pretreated Xiuyu stone powder;

[0083] S62, weigh the pretreated Xiuyu stone powder, activator and alkali co-solvent according to the ratio and mix them evenly. Among them, the weight percentage of Xiuyu stone powder is 70%, the weight percentage of the activator is 15%, and the weight percentage of the alkali co-solvent is 15%. The activator is a mixture of potassium carbonate and calcium carbonate and the ratio of the two is 1.2:1. The alkali co-solvent is potassium hydroxide;

[0084] S63, calcine the evenly mixed materials in a muffle furnace. The calcination conditions are: continuous calcination at 700 °C for 1.5 hours. After calcination, cool it and grind it to 200 meshes with a ball mill to obtain the soil acidification and heavy metal reduction conditioner;

[0085] S64, directly use the obtained soil acidification and heavy metal reduction conditioner as a powder product, or prepare it into a granular product by means of disk granulation, extrusion molding, or hot pressing molding. In this embodiment, the obtained soil acidification and heavy metal reduction conditioner is granulated by disk granulation.

[0086] Example 3

[0087] A combined remediation method for treating soil heavy metal pollution and preventing lodging of rice, comprising the following steps:

[0088] (1) Select a farmland area for safe utilization of heavy metal pollution in Jiangxi, with a soil pH value of 5.20 and a total cadmium content in the soil of 1.62 mg / Kg. The cadmium content in the soil of this area is higher than the screening value of agricultural land soil pollution risk in the "Soil Environmental Quality Standard" (GB15618-2018);

[0089] (2) Sow in early September of the first year. Use 2.5 Kg of seeds per mu of seedling land, evenly spread the seeds of Prunella vulgaris, and remove weeds regularly;

[0090] (3) Start thinning when the seedling height is 3 cm - 5 cm, remove weak seedlings and keep strong seedlings. When the seedlings grow to five leaves and one heart, they can be transplanted. The transplanting ends at the end of October, with a plant spacing of 25 cm × 30 cm;

[0091] (4) Harvest the medicinal parts of Prunella vulgaris with low heavy metal enrichment, namely the stems, leaves and flowers, in May of the following year;

[0092] (5) Harrow the soil and remove the roots of Prunella vulgaris with high heavy metal enrichment;

[0093] (6) 20 days before planting rice in the following year, apply the prepared soil acidification and heavy metal reduction conditioner. The application amount of the soil acidification and heavy metal reduction conditioner is 260 Kg / mu. The soil acidification and heavy metal reduction conditioner is composed of Xiuyu stone powder, activator and alkali co-solvent.

[0094] Among them, the soil acidification and heavy metal reduction conditioner is prepared through the following steps:

[0095] S61, crush the massive Xiuyu waste, pulverize it with a high-speed universal pulverizer and pass through a 100-mesh sieve to obtain pretreated Xiuyu stone powder;

[0096] S62, weigh the pretreated Xiuyu stone powder, activator and alkali co-solvent according to the ratio and mix them evenly. Among them, the weight percentage of Xiuyu stone powder is 65%, the weight percentage of the activator is 25%, and the weight percentage of the alkali co-solvent is 10%. The activator is a mixture of potassium carbonate and calcium carbonate and the ratio of the two is 1.4:1. The alkali co-solvent is sodium hydroxide;

[0097] S63, calcine the evenly mixed materials in a muffle furnace. The calcination conditions are: continuously calcine at 650 °C for 3.5 hours. After calcination, cool and grind to 200 meshes with a ball mill to obtain the soil acidification and heavy metal reduction conditioner;

[0098] S64. The obtained soil acidification and heavy metal reduction conditioner is directly used as a powder product, or is prepared into a granular product by means of disk granulation, extrusion molding, or hot pressing molding. In this embodiment, the obtained soil acidification and heavy metal reduction conditioner is directly used as a powder product.

[0099] The following experiments were conducted to verify the effects of the present invention.

[0100] In step (5) of Example 1, the soil was harrowed to remove the roots of Prunella vulgaris with high heavy metal enrichment. The roots, stems, leaves, spikes of Prunella vulgaris, as well as rhizosphere soil and non-rhizosphere soil were collected respectively, and the heavy metal contents were measured. The results are as Figure 2 、 Figure 3 shown.

[0101] According to the "Green Industry Standard for the Import and Export of Medicinal Plants and Preparations" of the Ministry of Commerce of the People's Republic of China, the heavy metal limit standards are as follows: lead (Pb) ≤ 5.00 mg / kg; cadmium (Cd) ≤ 0.3 mg / kg; mercury (Hg) ≤ 0.2 mg / kg; copper (Cu) ≤ 20.0 mg / kg; arsenic (As) < 2.0 mg / kg.

[0102] The over-standard element in this embodiment is cadmium ( Figure 2 ), and the other elements are all lower than the limit standards. It can be seen from Figure 2 that the order of heavy metal enrichment in different parts of Prunella vulgaris is root > stem > leaf > spike. The roots are highly enriched with heavy metals, the above-ground parts are less enriched, and the leaves and spikes are lower than the limit standards, having certain medicinal and economic values.

[0103] According to the "Soil Environmental Quality - Risk Control Standards for Soil Pollution of Agricultural Land", the heavy metal limit standards are as follows: lead (Pb) ≤ 80 mg / kg; cadmium (Cd) ≤ 0.3 mg / kg; mercury (Hg) ≤ 0.5 mg / kg; copper (Cu) ≤ 50 mg / kg; arsenic (As) < 30 mg / kg.

[0104] The over-standard element in this embodiment is cadmium ( Figure 3 ), and the other elements are all lower than the limit standards. It can be seen from Figure 3 that the cadmium content in rhizosphere soil is lower than that in non-rhizosphere soil, indicating that the roots of Prunella vulgaris can enrich heavy metals.

[0105] In addition, for the soil obtained in step (6) of Example 1, samples were taken from the soil, and the DTPA extraction method was used to conduct leaching experiments on the soil to detect the heavy metal contents after remediation. The measurement results are shown in Table 1:

[0106] Table 1 Heavy metal contents after remediation

[0107] Cadmium (Cd) Lead (Pb) Copper (Cu) pH Before treatment (mg / Kg) 0.47 22.84 60.85 5.50 After treatment (mg / Kg) 0.13 16.32 37.91 7.65

[0108] As can be seen from Table 1, the contents of cadmium, lead, and copper in the treated soil have all decreased compared with those before treatment, and are all lower than the risk screening values for agricultural land soil pollution in the "Soil Environmental Quality Standards" (GB15618-2018), and the soil pH value has also increased.

[0109] Please refer to Figure 4 , Figure 4 is the SEM image of the soil acidification and heavy metal reducing conditioner before (a) and after (b) adsorbing the heavy metal cadmium, lead, and copper complex pollution. From Figure 4 , it can be seen that a large number of stable short rod-shaped crystals can be observed on the surface of the material after adsorption, indicating the formation of precipitation.

[0110] Please refer to Figure 5 , Figure 5 is the FT-IR diagram (a) and XRD diagram (b) of the soil acidification and heavy metal reducing conditioner before and after adsorbing heavy metals. Among them, MSJ represents the material before adsorption, and MSJ-Cd-Pb-Cu represents the material after adsorbing the cadmium, lead, and copper complex pollution. From Figure 5 (a), it can be seen that the position of the infrared absorption peak has changed significantly after adsorption. At 3418 cm -1 and 615 cm -1 , the position of the peak related to the vibration of the hydroxyl group (-OH) has changed, indicating that they participate in the heavy metal adsorption process. At 1009 cm -1 and 892 cm -1 , the peaks can be attributed to the stretching vibration of Si-O. These peaks have changed significantly, indicating that Cd(II), Pb(II), and Cu(II) may have surface coordination with the unsaturated Si-O-Si bond. The absorption peak at 1426 cm -1 corresponds to CO3 2- , which may be due to the absorption of CO2 from the atmosphere and the reaction with MSJ to form carbonate groups. The shift of CO3 2- indicates that it may participate in the heavy metal adsorption process. The absorption peak near 1634 cm -1 corresponds to C=O / C=C, indicating that cation-Π bond complexation is also one of the adsorption mechanisms. From Figure 5 (b), it can be seen that the main phase of MSJ is Mg2SiO4, and no new phase is observed after adsorption, which may be because the generated conjugate is lower than the detection limit of XRD. In summary, the conditioner of the present invention can fix heavy metals through mechanisms such as adsorption, surface complexation, and precipitation.

[0111] In addition, based on the soil obtained in step (6) of Example 1, rice was planted in the present invention. Good rice seeds were selected and sown for seedling raising at the beginning of May. The seedling age was 25 days, and transplanting was completed at the end of May. The row spacing was 16.5 cm × 23 cm, and 3 - 4 plants were transplanted per hole. After 90% of the paddy was yellow and ripe, it was harvested on a sunny day. The rice was sampled by stem, leaf, and brown rice, blanched at 105°C, dried to a constant weight at 75°C, and after microwave digestion, the heavy metal content was measured by ICP - MS. The results are shown in Table 2:

[0112] Table 2 Cadmium, lead, and copper contents in different parts of rice plants

[0113] Stem (mg / Kg) Leaf (mg / Kg) Brown rice (mg / Kg) Cadmium (Cd) 0.102 0.016 0.017 Lead (Pb) 0.463 0.289 0.128 Copper (Cu) 4.434 3.561 2.468

[0114] According to the "National Food Safety Standard - Limits of Contaminants in Foods" (GB2762 - 2022), the heavy metal limit standards are as follows: cadmium (Cd) ≤ 0.2 mg / Kg, lead (Pb) ≤ 0.2 mg / Kg. As can be seen from Table 2, the cadmium and lead contents in brown rice are both lower than their limit standards and are within the safe range values.

[0115] In summary, according to the method for combined remediation of soil heavy metal pollution and rice lodging resistance provided by the present invention, the following beneficial effects are achieved:

[0116] (1) The present invention discloses a method for combined remediation of soil heavy metal pollution and rice lodging resistance. This method realizes the dry - wet rotation of Prunella vulgaris - rice through the planting of Prunella vulgaris and the repair of soil acidification and heavy metal reduction conditioner. The dry - wet rotation can improve the physical and chemical properties of the soil, solve the problem that the long - term application of passivators is prone to cause soil structure degradation, reduce pests and diseases, and improve crop yield and quality.

[0117] (2) The root exudates of Prunella vulgaris inhibit the absorption of heavy metals and improve the physical and chemical properties such as soil pH. The heavy metals in the soil can be removed by removing the roots of Prunella vulgaris.

[0118] (3) Among them, the soil acidification and heavy metal reduction conditioner contains serpentine powder. There are unsaturated Si - O - Si, O - Si - O bonds and magnesium bonds on the fracture surface of serpentine, which have high chemical activity and can interact with heavy metals through adsorption, chelation, etc. Its alkalinity can also solve the problem of soil acidification. In addition, serpentine is a silicate mineral containing a large amount of silicon, which can be absorbed by rice after activation, enhancing the lodging resistance of rice. It integrates the functions of soil acidification adjustment, heavy metal treatment, and rice lodging resistance.

[0119] (4) The serpentine raw material can be low - quality serpentine and its processing waste. The cost is low, and it does not contain harmful heavy metals or other harmful substances, which is conducive to resource recycling, turning waste into treasure, being environmentally friendly, and having good economic benefits.

[0120] (5) The preparation process of the present invention is simple, highly operable, saves manpower and material resources, and is easy to promote on a large scale.

[0121] (6) The present invention integrates functions of soil acidification adjustment, heavy metal treatment, and rice lodging resistance. Combining with the joint remediation of Prunella vulgaris-rice dry-wet rotation, it solves problems such as high costs for treating heavy metal pollution in acidified soil and serious rice lodging, and has no secondary pollution and good economic benefits.

[0122] The above-described embodiments merely represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed. However, it should not be construed as a limitation to the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims

1. A combined remediation method for soil heavy metal pollution and rice lodging resistance, characterized in that, It includes the following steps: (1) Select a heavy metal contaminated area for acidification remediation, and find the soil for safe utilization of heavy metal contaminated farmland according to the pH value and heavy metal content of the soil; (2) Sow in early September of the first year. Use 2.5 - 3 Kg of seeds per mu of seedling land, evenly broadcast the seeds of Prunella vulgaris, and remove weeds regularly; (3) Thin out the seedlings when the seedling height is 3 cm - 5 cm, remove the weak seedlings and keep the strong ones. When the seedlings grow to five leaves and one heart, they can be transplanted, and the transplantation ends at the end of October; (4) Harvest the medicinal parts of Prunella vulgaris with low heavy metal enrichment, namely the stems, leaves and flowers, in May of the following year; (5) Harrow the soil and remove the roots of Prunella vulgaris with high heavy metal enrichment; (6) 15 - 30 days before rice planting in the following year, apply the prepared soil acidification and heavy metal reduction conditioner, which is composed of Xiuyu stone powder, activator and alkali co-solvent; The soil acidification and heavy metal reduction conditioner is prepared through the following steps: S61, Crush the massive Xiuyu waste, pulverize it with a high-speed universal pulverizer and pass through a 100-mesh sieve to obtain the pretreated Xiuyu stone powder; S62, Weigh the pretreated Xiuyu stone powder, activator and alkali co-solvent according to the ratio and mix them evenly; S63, Calcinate the evenly mixed materials in a muffle furnace. After calcination, cool them and grind them to 200 meshes with a ball mill to obtain the soil acidification and heavy metal reduction conditioner; S64, Use the obtained soil acidification and heavy metal reduction conditioner directly as a powder product, or prepare it into a granular product by means of disk granulation, extrusion molding or hot pressing molding; In step S63, the conditions for muffle furnace calcination are: continuous calcination at 600 - 700 °C for 1.5 - 3.5 hours; In the soil acidification and heavy metal reduction conditioner, the weight percentage of Xiuyu stone powder is 60% - 70%, the weight percentage of activator is 15% - 32%, and the weight percentage of alkali co-solvent is 8% - 15%.

2. The combined remediation method for soil heavy metal pollution and rice lodging resistance according to claim 1, characterized in that, The activator is a mixture of potassium carbonate and calcium carbonate, and the ratio of the two is (1 - 1.4):

1.

3. The combined remediation method for soil heavy metal pollution and rice lodging resistance according to claim 1, characterized in that, The alkali co-solvent is one or more of sodium hydroxide and potassium hydroxide.

4. The combined remediation method for soil heavy metal pollution and rice lodging resistance according to claim 1, characterized in that, In step (6), the application amount of the soil acidification and heavy metal reduction conditioner is 200 - 300 Kg / mu.

5. The combined remediation method for soil heavy metal pollution and rice lodging resistance according to claim 1, characterized in that, Step (3) is specifically: Thin out the seedlings when the seedling height is 3 cm - 5 cm, remove the weak seedlings and keep the strong ones. When the seedlings grow to five leaves and one heart, they can be transplanted, and the transplantation ends at the end of October, with a plant spacing of 25 cm × 30 cm.

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