Remediation method suitable for high-background heavy metal polluted cultivated land in Xinjiang river basin

Abstract

The invention discloses a remediation method suitable for high-background heavy metal polluted cultivated land in the Xinjiang river basin. According to the heavy metal contaminated soil remediation method, harvesting and centralized treatment are conducted on plants through existing crop collecting equipment, after harvesting is completed, the collected plants are subjected to centralized composting, and after composting is completed, heavy metal impurities and overlarge-size plant straw existing in fertilizer are filtered out through filtering equipment; then the composted fertilizer is returned to the field and buried in the soil by 5-10 cm, it is guaranteed that the fertilizer is fully dissolved in the soil, the effect of recycling plants is achieved, and the problems that in an existing method, the used plants are directly discarded, space is occupied, the plants cannot be recycled, and the cost is low are solved. The problems that the environmental protection property of the process is affected, and meanwhile, after the polluted soil is purified by plants, the time for the polluted soil to stay on the land is long, so that the economical efficiency of later land utilization is affected, and the utilization rate of the whole land cannot be optimized are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation methods, and in particular to a remediation method suitable for cultivated land with high background heavy metal pollution in the Xinjiang River Basin. Background Art

[0002] Heavy metal pollution in soil is the most prominent environmental pollution problem in the field of agricultural planting. Heavy metal pollution in soil will cause changes in soil composition, structure and function, inhibit microbial activity, and gradually accumulate harmful substances or decomposition products in the soil, causing soil quality to decline and leading to plant growth and development disorders. Soil contaminated by heavy metals becomes a piece of "toxic land", which is indirectly absorbed by the human body through "soil → plant → human body" or "soil → water → human body", and ultimately endangers human health. The biological toxicity of heavy metal-contaminated soil depends on the bioavailability of heavy metals. Reducing the bioavailability of heavy metals is a key indicator of heavy metal-contaminated soil. In-situ passivation and phytoremediation are widely used to repair soil heavy metal pollution. In-situ passivation can change the form of soil heavy metals through adsorption, precipitation, complexation, etc., thereby reducing the bioavailability of heavy metals, while phytoremediation can use its super heavy metal enrichment ability to reduce the bioavailability of soil heavy metals.

[0003] The current restoration methods include the plant restoration method in the biological restoration method. This method plants are planted in the contaminated soil, relying on green plants to remove heavy metals (plant extraction and plant volatilization), or stabilize them in a harmless state (plant fixation and plant stabilization). Plants mainly repair heavy metal contaminated soil through absorption and transportation, and rhizosphere stabilization. However, there are still problems in the subsequent treatment of the purified plants. For example, after a large area of ​​plants are purified from the contaminated soil, they cannot be effectively and timely cleared out of the site, which makes subsequent agricultural planting difficult. Moreover, the plants are directly discarded after use, which not only takes up space, but also cannot be recycled, affecting the environmental friendliness of the process. At the same time, after the plants purify the contaminated soil, they remain on the land for a long time, which seriously delays the progress of the purification project and occupies too much time of cultivated land, thereby affecting the economy of the later land use and is not conducive to the optimal utilization rate of the entire land.

[0004] Therefore, in view of this, the inventor, based on his many years of rich experience in design, development and actual production in the related industry, has conducted research and improvements on the existing structures and deficiencies, and provided a method for remediating heavy metal contaminated soil, in order to achieve a more practical and valuable purpose. Summary of the invention

[0005] 1. Technical issues to be solved

[0006] In view of the deficiencies of the prior art, the present invention provides a remediation method applicable to arable land with high-background heavy metal pollution in the Xinjiang River Basin, which solves the problems that after large areas of plants purify polluted soil, they cannot be effectively and timely cleared from the site, resulting in difficulties in subsequent agricultural planting. Moreover, the used plants are directly discarded, which not only occupies space but also cannot be recycled, affecting the environmental friendliness of the process. At the same time, after the plants purify the polluted soil, they remain on the land for a long time, seriously delaying the progress of the purification project, occupying too much arable land time, thus affecting the economic efficiency of land use in the later stage and being unfavorable to the optimal utilization rate of the entire piece of land.

[0007] (II) Technical Solution

[0008] To achieve the above object, the present invention provides the following technical solution: A remediation method applicable to arable land with high-background heavy metal pollution in the Xinjiang River Basin, including S1. First, conduct a site investigation to determine the main pollutants and pollution degree of the polluted land. The soil pollutants mainly include arsenic, and there are also pollutants such as lead, zinc, and cadmium. Secondly, determine the physical and chemical properties of the soil and the soil pH value range, so as to fully consider the resistance, tolerance, and enrichment of remediation plants to these heavy metals, as well as the toxicity of acid pollution to remediation plants, and match suitable enrichment plants, alfalfa, to repair heavy metal composite pollution and acid-polluted soil. When planting grass, a soil remediation agent can be used to achieve the addition of a mineralizing agent, which is mainly used to change the composition of heavy metals in the soil. The soil remediation agent is prepared by mixing ferrous sulfate and sulfate-type calcium-aluminum hydrotalcite in a ratio of 2:1;

[0009] S2. Then, after determining the type of plants to be planted, use a seedling-raising device to first cultivate them indoors. After the plants germinate and reach 1 mm to 5 mm, they can be packed. Then, rototill the polluted land, with the rototilling depth being 30 cm to 50 cm. Then, evenly sow the packed plant seeds into the rototilled polluted soil through a sowing device, and ensure that the number of plants sown per square meter is within the range of 100 to 200;

[0010] S3. At the same time, after sowing the plant seeds, conduct deep irrigation to ensure that the water volume per square meter is within the range of 10 L to 15 L. Then, cover the surface of the seeds with a thin soil layer of 1 mm to 1 cm to promote the subsequent rooting and continued growth of the plants, and further improve the survival rate of the plants in the overall area;

[0011] S4. Next, when the plant grows into maturity and its height ranges from 50 cm to 1 m, it is the peak period for the plant to absorb harmful substances. The process of the plant purifying and adsorbing heavy metals in the soil generally includes three categories: The first is phytoextraction: Phytoextraction, also known as phytoremediation, refers to the use of hyperaccumulator plants with strong heavy metal enrichment ability to absorb heavy metal pollutants in the soil, and then transfer and store them in the above-ground parts such as the stems and leaves of the plant. By harvesting the above-ground parts and conducting centralized treatment, the purpose of removing or reducing heavy metal pollutants in the soil can be achieved. Plants that meet phytoextraction have the following characteristics: fast growth, large biomass, the ability to accumulate several heavy metals simultaneously, high enrichment efficiency, strong plant tolerance, and the ability to accumulate high concentrations of pollutants in the body. The second is phytostabilization: Using the absorption, chelation, complexation, precipitation, decomposition, redox and other processes of special plants to passivate or fix a large amount of toxic heavy metals in the soil, so as to reduce their bioavailability and mobility, thereby reducing the harm of their pollutants to organisms and the environment. The third is phytovolatilization: Phytovolatilization refers to the way that plants use their own functions to absorb heavy metals in the soil into their bodies and turn them into volatile forms and release them into the atmosphere, so as to achieve the removal of heavy metals in the soil;

[0012] S5. Next, when the purification time of the adult plant for the contaminated soil reaches three to six months, the existing crop collection equipment can be used to harvest and centrally process the plants. After the harvesting is completed, the collected plants are composted centrally. After the composting is completed, the filter equipment filters out the heavy metal impurities and overly large plant straws existing in the fertilizer, and then the composted fertilizer is returned to the field and buried 5 to 10 cm into the soil to ensure the full dissolution of the fertilizer into the soil;

[0013] S6. At the same time, after collecting the plants, they can also be packaged and dried to keep their moisture content within 5% to 3%, and then carbonized, and then sent to a thermal power plant for thermal power generation;

[0014] S7. In the later stage, within one to three months after the fertilizer is returned to the field, every week, the existing detection equipment is used to measure and record the content of various heavy metals and the pH value in the soil. When all indicators tend to be within the normal range, normal agricultural planting work can be carried out;

[0015] S8. At the same time, during planting, soil samples are taken and detected every six months or at the time when each crop grows and matures, so as to effectively detect the subsequent various values of the soil in real time, ensure that subsequent pollution incidents will not occur repeatedly, thereby maximizing the planting function of the soil, improving the economic benefits of crops, and reducing the vacant time of the land.

[0016] Preferably, in step S1, a small amount of soil sample is taken first and placed at the bottom of a bowl. Then, 4 - 6 drops of distilled water are added, and the mixture is stirred evenly with a glass rod. After it stands and clarifies, a general test paper is immersed in the clear liquid, and the test paper changes color. Then, the colored test paper is compared with the pH standard colorimetric card to directly obtain the pH value, which is then recorded.

[0017] Preferably, in step S2, first prepare the materials, including seeds, seedling soil, watering can, tweezers, seedling trays or small flower pots, and pots (buckets). Then, mix the soil. The sowing soil is mixed with water before use. Pour the seedling soil into the pot (bucket) and stir while watering. Control the soil humidity so that it does not drip when held in the hand. Then, fill the soil into the seedling tray and press it slightly, but do not press it too tightly because the seeds need to breathe. Then, leave it natural.

[0018] Preferably, in step S3, the ungerminated embryo seeds can be picked out manually, and then the selected germinated seeds are sown and covered with soil. At the same time, the ungerminated seeds can be re - nursed to ensure that seeds with different hypnosis times can all germinate completely and ensure the germination rate.

[0019] Preferably, in step S4, observe once every week to ensure that the growth of plants in each area is good. Apply fertilizer and hoe the soil in time for weak seedlings, and promptly replant the blank areas to ensure the overall purification coverage rate of the soil.

[0020] Preferably, in step S6, the biomass straw raw materials go through complex processes such as drying, modification, mixing, forming, and carbonization to continuously produce fuel, which can be packaged and transported later to supply various burners, biomass boilers, melting furnaces, and biomass power generation.

[0021] (III) Beneficial effects

[0022] The present invention provides a remediation method applicable to high - background heavy - metal - polluted cultivated land in the Xinjiang River Basin, having the following beneficial effects:

[0023] (1) This method for remediating heavy metal - contaminated soil involves using existing crop collection equipment to harvest and centrally process plants. After harvesting, the collected plants are composted. After composting, a filtration device filters out heavy metal impurities and overly large plant straws present in the fertilizer. Then, the composted fertilizer is returned to the field and buried 5 to 10 centimeters deep into the soil to ensure the full dissolution of the fertilizer into the soil interior, achieving the effect of recycling and reusing the plants. It solves the problem that in existing methods, the used plants are directly discarded, which not only occupies space but also cannot be recycled, affecting the environmental friendliness of the process. At the same time, after the plants purify the contaminated soil, they remain on the land for a long time, seriously delaying the progress of the purification project, occupying too much arable land time, thus affecting the economic efficiency of subsequent land use and being unfavorable to the optimal utilization rate of the entire land.

[0024] (2) This method for remediating heavy metal - contaminated soil, after seedling raising, manually picks out the ungerminated embryos, and then sows and buries the selected germinated seeds. At the same time, the ungerminated seeds can be re - nursed to ensure that seeds with different hypnosis times can all germinate completely, guaranteeing the germination rate. It can effectively avoid the problem of large - scale local blank blocks during sowing, and at the same time reduce the seed cost of the equipment, increasing the economic efficiency of seedling raising in this method. Specific implementation method

[0025] Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by the present invention.

[0026] The present invention provides a technical solution: a method for remediating high - background heavy metal - contaminated arable land in the Xinjiang River Basin.

[0027] It includes the following steps: S1. First, conduct a site survey to determine the main pollutants and pollution degree of the contaminated land. The soil pollutants mainly include arsenic, and there are also pollutants such as lead, zinc, and cadmium. Secondly, determine the physical and chemical properties of the soil and the soil pH value range, so as to fully consider the resistance, tolerance, and enrichment of remediation plants to these heavy metals, as well as the toxicity of acid pollution to remediation plants. Appropriate enrichment plant alfalfa is selected to repair heavy metal - compound - polluted and acid - polluted soil. When sowing grass, a soil remediation agent can be used to add a mineralizing agent, which is mainly used to change the composition of heavy metals in the soil. The soil remediation agent is prepared by mixing ferrous sulfate and sulfate - type calcium - aluminum hydrotalcite in a ratio of 2:1.

[0028] S2. Next, after determining the type of plants to be grown, use a seedling-raising device to first cultivate them indoors. After the plants germinate and reach a height of 1 to 5 millimeters, they can be packed. Then, rototill the polluted land to a depth of 30 to 50 centimeters. Next, evenly sow the packed plant sprouts into the rototilled polluted soil through a sowing device, and ensure that the number of plants sown per square meter is within the range of 100 to 200 plants;

[0029] S3. At the same time, after sowing the plant sprouts, conduct deep irrigation to ensure that the water volume per square meter is within the range of 10 to 15 liters. Then, cover the surface of the sprouts with a thin soil layer of 1 millimeter to 1 centimeter to promote the subsequent rooting and continued growth of the plants, and further improve the survival rate of the overall plants;

[0030] S4. Then, when the plants grow into maturity and reach a height of 50 centimeters to 1 meter, it is the peak period of the efficiency of the plants absorbing harmful substances. The process of the plants purifying and adsorbing heavy metals in the soil generally includes three categories: The first category is phytoextraction: Phytoextraction, also known as phytoremediation, refers to using hyperaccumulator plants with strong heavy metal enrichment ability to absorb heavy metal pollutants in the soil, and then transfer and store them in the above-ground parts such as the stems and leaves of the plants. By harvesting the above-ground parts and conducting centralized treatment, the purpose of removing or reducing heavy metal pollutants in the soil can be achieved. Plants that meet phytoextraction have the following characteristics: fast growth, large biomass, ability to accumulate several heavy metals simultaneously, high enrichment efficiency, strong plant tolerance, and ability to accumulate high concentrations of pollutants in the body. The second category is phytostabilization: Using the absorption, chelation, complexation, precipitation, decomposition, oxidation-reduction and other processes of special plants to passivate or fix a large amount of toxic heavy metals in the soil, so as to reduce their bioavailability and mobility, thereby reducing the harm of their pollutants to organisms and the environment. The third category is phytovolatilization: Phytovolatilization refers to the way that plants use their own functions to absorb heavy metals in the soil into their bodies and turn them into volatile forms and release them into the atmosphere, so as to achieve the removal of heavy metals in the soil;

[0031] S5. Then, when the adult plants have purified the polluted soil for three to six months, the plants can be harvested and centrally processed using existing crop collection equipment. After the harvesting is completed, the collected plants are centrally composted. After the composting is completed, filter out the heavy metal impurities and overly large plant straws in the fertilizer through a filtering device, and then return the composted fertilizer to the field and bury it 5 to 10 centimeters into the soil to ensure the full dissolution of the fertilizer into the soil;

[0032] S6. At the same time, after collecting the plants, the plants can also be packed and dried to keep their moisture content within 5% to 3%, and then carbonized, and then sent to a thermal power plant for thermal power generation;

[0033] S7. In the later stage, within one to three months after returning the fertilizer to the field, every week, use existing detection equipment to measure and record the content of various heavy metals and the pH value in the soil. When all indicators tend to be within the normal range, agricultural planting work can be carried out normally;

[0034] S8. At the same time during planting, take soil samples for detection every six months or at the time when each crop grows and matures in a season to effectively detect the subsequent values of the soil in real time, so as to ensure that subsequent pollution incidents will not occur repeatedly, thereby maximizing the planting function of the soil, improving the economic benefits of crops, and reducing the vacant time of the land.

[0035] Among them, the plants can choose the composite planting method of rice + alfalfa. Alfalfa can be planted after the rice planting is completed. The planting process of rice is as follows:

[0036] Seed selection: Select high-quality, disease-resistant and high-yielding varieties according to the accumulated temperature, soil and growth environment of the local area;

[0037] Seed sunning: Select the selected seeds and sun them in the sun for 2 - 3 days on a sunny day to break the seed dormancy, enhance the enzyme activity, and improve the germination potential and germination rate of the seeds;

[0038] Seed cleaning: Select the sunned seeds with 23% yellow mud water or 12 - 13% brine. That is, dry the loess in advance, then add a small amount of water to make a paste and then add water to adjust it. When a fresh egg floats on the water surface to the size of a 5-cent coin, add the seeds. After fishing out the shriveled grains, wash them with clean water once and then disinfect them. If the seeds have been selected by specific gravity, they can be directly disinfected;

[0039] Disinfection and seed soaking: Immerse the cleaned seeds in the prochloraz solution and stir once a day. It is required to reach an accumulated temperature of 100 degrees. That is, soak the seeds at a water temperature of 10 degrees for 10 days, at a water temperature of 15 degrees for 7 days, and at a water temperature of 20 degrees for 5 days to absorb enough water, so that the seeds can ensure uniform and strong germination. Otherwise, it is very easy to heat up when the seeds do not germinate, resulting in the phenomenon of burning the seeds and making the seeds lose their germination ability;

[0040] Germination promotion process: Warm up the soaked seeds with 50-degree warm water, place them on 30 cm thick straw, wrap them with a plastic cloth, and cover them with a cotton quilt. Control the temperature at 30 - 32 degrees. Stir regularly to ensure uniform temperature. After about 36 hours or 48 hours, when 80% of the seeds show white tips, it is called breaking the chest. After breaking the chest, lower the temperature to 25 degrees for germination promotion. When 80% of the seeds have a bud length of 3 mm and a root length of 5 mm, cool the buds at room temperature (i.e., the indoor temperature) for 6 - 8 hours and then they can be sown;

[0041] Sowing process: Sow thinly to raise strong seedlings, with the seeding rate being "better sparse than dense". Optimal sowing period: If the shed is covered to raise the temperature on March 10th, sowing can be carried out from April 5th to 10th; for medium-sized sheds, it can be from April 15th to 20th. The seeding rate should be determined according to the seedling age. If the seeds germinate on April 15th and are transplanted on May 15th, with a germination rate above 90%, 0.24 catties of dry seeds can be sown per tray. After sowing, use wooden chips to press the seeds into the soil on three sides until they are flush with the ground, and then cover with 1 cm of sifted soil.

[0042] Seedbed management: Raise strong seedlings with low temperature and less water: The temperature in the seedbed should be "better low than high". The specific temperature should be controlled at 28 degrees when the seedlings emerge evenly, 25 degrees at the 1.1-leaf stage, 23 degrees at the 2.1-leaf stage, 21 degrees at the 3.1-leaf stage, and 20 degrees thereafter. Three to five days before transplanting, uncover the cloth day and night for hardening the seedlings. If the temperature drops below 4 degrees at night, cover the cloth again to prevent frost damage. The humidity in the seedbed should be "better dry than wet". Generally, there will be no water shortage after the seedlings emerge evenly. It is normal when there is a dry soil layer of 0.5 cm on the surface of the bed soil and the underlying bed soil is soft and moist. If the roots of the seedlings are well-developed with many white roots, and the leaf tips spit less water in the morning and wilt at noon, and when the seedlings are pulled out, there are only white roots and no wet soil around the roots, it means there is a real water shortage, and in this case, a thorough watering should be done in the early morning; on the contrary, if the seedlings wilt, it means there is a damping-off disease. It is necessary to understand the condition, determine whether it is fungal or physiological, and administer the right medicine for timely treatment;

[0043] Transplant in a timely manner: Spray insect repellents and antifreeze agents 1 - 2 days before transplanting. When the temperature stabilizes at 13 degrees for three consecutive days, start transplanting. Transplanting can start on May 12th in the second accumulated temperature zone. Transplanting can start on May 15th in the third accumulated temperature zone (try to transplant as early as possible under the condition of ensuring no frost damage to strive for effective accumulated temperature, promote early maturity, and achieve high yields). When transplanting, the water layer should cover at least 50 - 80% of the field surface. And transplant from the lower pond to the upper pond. When half of the pond is transplanted, drain the excess water from the upper pond into the transplanted pond. This can save water, prevent frost damage, and promote quick greening. The row spacing is one-third of the plant height, which is the most reasonable. The hill spacing is determined according to the tillering strength of the variety. Generally, transplant at 9x3 or 9×4, with 4 - 6 plants per hill. The transplanting depth should be based on not floating the seedlings, and the shallower the better. In addition, transplanting can also be carried out according to the leaf age. Starting from the 3.2-leaf stage and ending at the 4.5-leaf stage is the best period. Transplanting too early will result in poor root coiling of the seedlings, and transplanting too late will cause slow greening and early ear emergence;

[0044] Rational fertilization:

[0045] Based on soil testing and analysis conducted over many years, across multiple plots and on multiple occasions, the soil shows sufficient phosphorus but lacks potassium, and has a relatively low nitrogen content. Therefore, nitrogen should be supplemented, phosphorus should be stabilized, and potassium should be increased. Fertilization should be carried out according to the leaf age. The base fertilizer should be applied before plowing the land, at a rate of 35 - 40 catties per mu. The green-recovery fertilizer should be applied 7 - 10 days after transplanting, based on the emergence of new roots in the seedlings, at a rate of 15 - 20 catties per mu of special green-recovery fertilizer. At the end of the jointing stage, 14 - 18 catties of special panicle fertilizer should be applied per mu. Under normal circumstances, 45 - 50 days after transplanting (if transplanting is done on May 15th, it should be around July 1 - 5th), the panicle fertilizer should also be applied considering the weather, soil conditions, and seedling growth;

[0046] Scientific water management:

[0047] "Water is both the life and the disease of rice." It should follow the principle of being shallow in the early stage, having sunning in the middle stage, and being moist in the later stage, with just enough physiological and ecological water. That is, after transplanting, the paddy field surface should be kept without exposure. During tillering, an inch of water is appropriate. At the end of tillering, the field should be sunned to improve air permeability and oxygen supply, thus enhancing the root vitality. Fertile fields or those with vigorous growth should be sunned for a few more days. Conversely, less or no sunning is required, and then a water layer of 5 - 6 centimeters should be irrigated. At this time, as the plants start to joint, the fertilizer and water should not be excessive, otherwise it is easy to become overly lush and lodging. After the first and second nodes are pulled out, the water layer should be deepened to 3 inches for deep water ear formation. Two days before heading, the water should be drained appropriately for ventilation and oxygen supply to maintain the vitality of the last four leaves. Water should not be lacking from the start of heading to full heading, otherwise it will affect heading. After full heading to the dough stage, intermittent irrigation can be carried out, that is, the previous water should not see the next water, with dry and wet alternation. After the yellow ripening stage, drainage should start.

[0048] Pest and disease control:

[0049] Diseases: Seedling blight and late rice blast are the key factors affecting rice yield.

[0050] Blight is divided into fungal and physiological diseases. In recent years, most of the blight cases are physiological. The main causes are improper management, poor environment and other factors. Excessive moisture in the seedbed soil, low seedbed temperature, hardening of the seedbed soil and poor air permeability are the reasons for the disease. Secondly, excessive alkalinity in the seedbed soil is conducive to the reproduction of pathogens. In addition, excessive and frequent watering, excessive nitrogen fertilizer, uneven fertilization, excessive seeding rate, premature seeding, too high seedbed temperature, and insufficient ventilation and hardening of seedlings may all cause the disease;

[0051] Control methods: Disinfect the seedbed before sowing, adjust the acidity of the seedbed soil to make the pH value between 5 - 5.5. After emergence, ventilation and hardening of seedlings should be carried out in a timely manner. Uncover the cloth at 10 am and cover it at 2 pm to reduce the temperature difference. Spray disease prevention agents at the 1.5-leaf stage. If the disease is found, the cause must be identified clearly, the environment improved, and the right medicine applied. Observe regularly and strive to transplant seedlings earlier.

[0052] Rice blast can be divided into seedling blast, leaf blast, node blast, neck blast, panicle blast, and grain blast. Prevention should be the main focus. First, select disease-resistant varieties and manage them scientifically with reasonable fertilization. Second, carry out timely drug prevention. Generally, spraying medicine once between July 15th and 25th can prevent leaf blast and node blast, and spraying once 1 - 2 days before heading can prevent panicle neck blast. If the disease is found, spray once again after full heading;

[0053] Pests: The leaf miner in the seedling stage and the striped stem borer in the later stage have the greatest impact on rice yield.

[0054] For the leaf miner, insect-proof agents can be sprayed 1 - 2 days before transplanting (this is convenient, economical, and has a good effect). Otherwise, insect-proof agents must be sprayed 10 - 15 days after transplanting. Otherwise, once the pest occurs, the damaged leaves will be completely eaten up in 2 - 3 days, affecting the growth and development for 5 - 7 days;

[0055] Prevention should be the main focus for the striped stem borer because the larvae bore into the rice plants to feed. When you find the damaged parts (such as withered sheaths, withered hearts, white panicles), it is very difficult to penetrate the interior of the plants with pesticides to kill the pests, resulting in phenomena such as lodging, dead stalks, and dead panicles. When milling rice, there will be an increase in broken rice, dead rice, and black-tipped rice, a decrease in the milling rate, and a decline in efficiency. This cannot be ignored, and it should be sprayed once each between July 15th - 20th and August 5th - 10th. It is best to spray when adult insects (i.e., moths) are flying in the field;

[0056] Harvesting at maturity: Harvest at the right time. Many rice farmers think that the riper the rice, the higher the milling rate, so they delay harvesting. This results in more cracked grains, broken rice, and a reduction in head rice. Due to over-ripening, sugar is lost and starch increases, leading to a decline in quality. Therefore, harvest at the right time according to different varieties. Rice maturity is divided into milk ripening, wax ripening, yellow ripening, full ripening, and withered ripening. At the full ripening stage (i.e., when 98% of the grains in the rice panicle are white and 2% are green, or when 45 - 50 days have passed since full heading), it is the harvesting period with the highest milling rate and the best quality.

[0057] The planting process of alfalfa is as follows: The main propagation method of alfalfa is seed propagation.

[0058] Preparations before sowing:

[0059] The most suitable land for selection is neutral or slightly alkaline soil with deep and loose soil layers, convenient drainage and irrigation, and a pH value of 6.5 - 7.5. It can also grow well on saline-alkali land with a soil salt content of 0.2%. Prepare the land finely and thoroughly remove weeds. For spring sowing, after the previous year's forage or crop is harvested, shallow tillage is carried out to kill the stubble, remove weeds, and conserve soil moisture. Then, deep plow to a depth of 20 cm, and then harrow and roll to make it flat. Base fertilizer should be applied in combination with land preparation. The base fertilizer can be a certain amount of farmyard manure and various nitrogen, phosphorus, and potassium fertilizers;

[0060] Sowing:

[0061] Seeds should be cleaned and dried to make the seed purity reach 90%. Before sowing, pesticides, herbicides, rhizobia and fertilizers can be mixed with seeds in proportion to avoid diseases and pests in the seedling stage. Mixing seeds with bacterial fertilizers such as rhizobia, 1 kg of rhizobia can be mixed with 10 kg of seeds, which can increase the yield by more than 20%. Alfalfa sowing period can be chosen in spring or summer. Spring sowing can be done in places with good soil moisture and little wind and sand damage in spring; summer sowing is appropriate in places with dry soil, large wind and sand and late final frost period in spring. It is best to sow before the rainy season arrives at the end of June, which is conducive to sowing and preserving seedlings at one time. Alfalfa sowing is generally done by row sowing or ridge sowing, with a row spacing of 30-60 cm. Ridge sowing adopts dense ridges and sparse planting, with a row spacing of 15-20 cm, which not only increases coverage, increases yield, but also facilitates field management. The seed amount per mu is 0.75-1.00 kg, and the sowing amount can be appropriately increased or decreased according to the seed quality and different plots. Alfalfa seeds are very small, so the best depth of soil covering is about 2 cm. If the soil is loose, compact it before sowing to help control the depth; compact it again after sowing to help retain moisture;

[0062] Field management:

[0063] After sowing, check the seedlings and replant in time to ensure the planting density. Irrigation can be carried out in droughts in places with conditions. Both furrow irrigation and sprinkler irrigation are available, but sprinkler irrigation is preferred. The root system of alfalfa cannot tolerate flooding. 24 hours of flooding will cause death. In the rainy season, attention should be paid to draining the water from the low-lying areas in the field in time. Organic fertilizer should be applied as base fertilizer before sowing, and some phosphorus and potassium fertilizers should be applied appropriately;

[0064] Alfalfa grows very slowly in the seedling stage and is easily attacked by weeds. Weeding is required during the seedling stage, after the plant turns green, and before and after mowing. Chemical herbicides are divided into soil treatment herbicides applied before sowing, herbicides applied before seedlings, and herbicides applied after seedlings. However, it should be noted that the drug effect will expire 2-3 weeks before mowing to avoid poisoning of livestock;

[0065] Alfalfa can be mowed 2-3 times a year. The first mowing is most suitable during the early flowering period, when the protein content is the highest. It should not be mowed later than the peak flowering period, otherwise the leaves will fall severely, the stems will become fibrous, and the quality will decline. The stubble height is generally about 5 cm. The last mowing should be about 30 days before the early frost, and the stubble height should be 7-8 cm to facilitate wintering. The mowed alfalfa should be dried in the shade and baled and stored in time, otherwise it will fall leaves if it is too dry, affecting the quality of the grass.

[0066] Among them, alfalfa can reach 30cm to 50cm in the second year after planting, and mineralizers (sulfate-type calcium-molybdenum or calcium-iron hydrotalcite) are spread in April of the second year after planting, and then the soil is plowed into the soil. The composite planting method of rice + alfalfa can be adopted to carry out an organic and natural soil restoration operation process to achieve the purpose of repairing heavy metal-contaminated farmland in the context of the Xinjiang River Basin.

[0067] Working principle: By relying on green plants to remove heavy metals (phytoremediation and phytovolatilization), or to stabilize them into a harmless state (phytostabilization and phytoimmobilization), plants mainly repair heavy metal contaminated soil through two ways: absorption and transportation, and rhizosphere stabilization. Phytostabilization is to use methods such as root adsorption, precipitation, rhizosphere complexation or metal reduction to reduce the mobility of heavy metals in the soil and reduce the possibility of their entry into the food chain. This process of phytostabilization mainly occurs in the rhizosphere area, where the stable and activated states of heavy metals are directly affected by nutrients, enzyme activities and rhizosphere microorganisms in the rhizosphere environment. For severely heavy metal contaminated soil, phytostabilization can be combined with stabilization methods to ensure the thoroughness of soil purification work and the final purification effect.

[0068] In summary, by using existing crop collection equipment to harvest and centrally process plants, after the harvesting is completed, the collected plants are composted centrally. After the composting is completed, filtering equipment is used to filter out heavy metal impurities and overly large plant straws existing in the fertilizer. Then, the composted fertilizer is returned to the field and buried 5 to 10 centimeters deep into the soil to ensure the full dissolution of the fertilizer into the soil interior, achieving the effect of recycling and reusing the plants. This solves the problem that in the existing methods, the used plants are directly discarded, which not only occupies space but also cannot be recycled, affecting the environmental protection of this process. At the same time, after the plants purify the contaminated soil, they stay on the land for a long time, seriously delaying the progress of the purification project, occupying too much time of the cultivated land, thus affecting the economy of the subsequent land use and being unfavorable to the optimal utilization rate of the whole piece of land.

[0069] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0070] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for remediating farmland with high background heavy metal pollution in the Xinjiang River Basin, characterized by: include, S1. First, conduct a site survey to determine the main pollutants and degree of contamination of the land. Soil pollutants mainly include arsenic, and other pollutants such as lead, zinc and cadmium. Secondly, determine the physical and chemical properties of the soil and the pH range of the soil, so as to fully consider the resistance, tolerance and enrichment of the restoration plants to these heavy metals, as well as the toxicity of acid pollution to the restoration plants. Match the appropriate enrichment plant alfalfa to repair the heavy metal compound pollution and acid pollution of the soil. While planting grass, you can use soil remediation agents to achieve the addition of mineralizers, which are mainly used to change the heavy metal composition of the soil. The soil remediation agent is made of ferrous sulfate and sulfate-type calcium aluminum hydrotalcite in a ratio of 2:1; S2. After determining the type of plant to be planted, use seedling raising equipment to first cultivate it indoors. After the plants germinate and reach one to five millimeters, they can be packaged, and then the contaminated land is rotary tilled to a depth of thirty to fifty centimeters. Then, the packaged plant buds are sequentially and evenly sown into the contaminated soil after rotary tillage through sowing equipment, and the number of plants sown in one square meter is guaranteed to be within the range of 100 to 200 plants; S3. After sowing the plant seeds, deep irrigation is carried out to ensure that the water volume per square meter is within the range of ten to fifteen liters. Then, a thin layer of soil of one millimeter to one centimeter is covered on the surface of the seeds to promote the subsequent rooting and continued growth of the plants, and further improve the survival rate of the plants in the overall range.

2. According to claim 1, a method for repairing farmland with high background heavy metal pollution in the Xinjiang River Basin further comprises the following steps: S4. When the plant grows into a mature adult and its height is between 50 centimeters and 1 meter, the efficiency of the plant in absorbing harmful substances reaches its peak. The process of plant purification and adsorption of heavy metals in the soil can be roughly divided into three categories: The first type of plant extraction: Plant extraction, also known as plant extraction, refers to the use of hyperaccumulators with strong heavy metal enrichment ability to absorb heavy metal pollutants in the soil, and then transfer and store them to the above-ground parts such as plant stems and leaves. By harvesting the above-ground parts and conducting centralized treatment, the purpose of removing or reducing heavy metal pollutants in the soil is achieved. Plants that meet the requirements of plant extraction have the following characteristics: fast growth and large biomass. , can accumulate several heavy metals at the same time, has a high enrichment efficiency, strong plant tolerance, can accumulate high concentrations of pollutants in the body, the second type of plant fixation: using special plants' absorption, chelation, complexation, precipitation, decomposition, oxidation-reduction and other processes to passivate or fix a large number of toxic heavy metals in the soil to reduce their biological effectiveness and mobility, thereby reducing the harm of pollutants to organisms and the environment, the third type of plant volatilization: plant volatilization refers to the use of its own functions to absorb heavy metals in the soil into the body, and convert them into volatile forms and release them into the atmosphere, thereby achieving a way to remove heavy metals in the soil; S5. When the adult plants have been contaminating the polluted soil for three to six months, the plants can be harvested and processed using existing crop collection equipment. After harvesting, the collected plants are concentrated for composting. After composting, the filtering equipment is used to filter out the heavy metal impurities and excessively large plant stalks in the fertilizer. The composted fertilizer is then returned to the field and buried five to ten centimeters deep in the soil to ensure that the fertilizer is fully dissolved in the soil. S6. At the same time, after the plants are collected, they can be packaged and dried to keep their moisture content within 5% to 3%, and then carbonized and then sent to a thermal power plant for thermal power generation; S7. In the later period, within one to three months after returning the fertilizer to the field, the heavy metal content and pH value in the soil are measured and recorded every week using existing testing equipment. When all indicators are within the normal range, agricultural planting can be carried out normally. S8. At the same time, during planting, soil sampling and testing should be carried out every six months or one season when crops grow and mature, so as to effectively test the subsequent soil values ​​in real time to ensure that subsequent pollution incidents will not recur, thereby maximizing the use of soil for planting, improving the economic benefits of crops, and reducing the vacant time of land.

3. A method for repairing farmland with high background heavy metal pollution in the Xinjiang River Basin according to claim 2, characterized in that: In step S2, you can first take a small amount of sample soil and put it in the bottom of a bowl, then add 4 to 6 drops of distilled water, stir it thoroughly with a glass rod, wait for it to stand and clarify, immerse a general test paper in the clear liquid, the test paper will change color, then compare the color-changed test paper with the pH standard colorimetric card, that is, directly obtain the pH value, and then record it.

4. A method for repairing farmland with high background heavy metal pollution in the Xinjiang River Basin according to claim 2, characterized in that: In step S3, first prepare the materials, including seeds, seedling soil, watering can, tweezers, seedling hole pots or small flower pots, basins (buckets), then mix the soil. Mix the sowing soil with water before use. Pour the seedling soil into the basin (bucket) and stir it with a sprinkler. The humidity of the soil is controlled so that it does not drip when held in the hand. Then fill the soil. Put the soil into the seedling tray and press it slightly, but not too tightly. The seeds need to breathe and then germinate naturally.

5. The method for repairing farmland with high background heavy metal pollution in the Xinjiang River Basin according to claim 2, characterized in that: In step S4, the ungerminated embryo seeds can be manually picked out, and then the screened seed buds can be sown and buried in the soil. At the same time, the ungerminated seeds can be raised for a second time to ensure that the seeds with different hypnosis times can fully germinate and ensure the germination rate.

6. A method for repairing farmland with high background heavy metal pollution in the Xinjiang River Basin according to claim 2, characterized in that: In step S5, observations are conducted every week to ensure that the plants in each area are growing well, weak seedlings are fertilized and hoeed in time, and blank areas are replanted in time to ensure the overall soil purification coverage.

7. The method for repairing farmland with high background heavy metal pollution in the Xinjiang River Basin according to claim 2, characterized in that: In step S6, the biomass straw raw materials undergo a complex process of drying, conversion, mixing, molding, carbonization, etc., so as to continuously produce fuel, which can be packaged and transported later to provide various burners, biomass boilers, melting furnaces, and biomass power generation.