Method for decomposing toxic weeds, feeding back, promoting carbon and increasing sink

Abstract

A method for decomposing toxic weeds, feeding back, promoting carbon and increasing sink relates to the technical field of toxic weed recycling, and comprises the steps of collecting toxic weeds in a sample plot, crushing the toxic weeds, establishing a treatment point, mixing and adding nanoscale ferrihydrite, performing short-term high-temperature decomposition, performing natural decomposition, feeding back and the like. The toxic weeds are accelerated to be decomposed and then fed back to the collection land, so that the soil fertility of the collection land is improved. Besides, by adopting the method provided by the invention, carbon loss caused by release of toxic weeds in the form of CO2 in the degradation process can be reduced, so that the content of organic carbon in soil is remarkably increased. The method can effectively treat common toxic weeds such as lacquer trees, nettle, alocasia macrorrhiza, ambrosia trifida and the like, and has a relatively good application range.

Description

Technical Field

[0001] The invention relates to the field of resource utilization of poisonous weeds, and in particular to a method for promoting carbon sink by composting and feeding poisonous weeds. Background Art

[0002] Poisonous weeds refer to poisonous plants that grow on grasslands. They are mainly distributed in arid or humid areas. Common poisonous weeds include sumac, nettle, calla lily, and three-lobed ragweed. Most grassland poisonous weeds have stems, leaves, and flowers, and they also produce some toxic substances, such as organic acids, amino acids, and polyphenol compounds, with different toxicities. Their toxins are harmful to animals, especially livestock and poultry. When livestock eat these plants and seeds, they will suffer from indigestion, vomiting, diarrhea, allergic symptoms, arthritis, and muscle cramps. In extreme cases, their toxins may also cause severe poisoning and death. Although poisonous weeds have potential hazards, if appropriate measures are taken, they can be effectively avoided from harm. At the same time, they should be protected to maintain the integrity of the grassland ecological environment.

[0003] The above-ground vegetation layer, underground root layer and soil layer of grassland are the three most important carbon pools of grassland. Grassland ecosystem absorbs carbon dioxide from the atmosphere through photosynthesis, and fixes carbon in grassland plants and grassland soil in the form of organic carbon, thus forming a "carbon container" of grassland ecosystem. Its total carbon storage accounts for about 30% to 34% of the total terrestrial ecosystem, which is the second largest carbon pool on land after forests. Compared with forest ecosystems, grasslands have higher vegetation coverage and shorter vegetation growth cycles, and have huge carbon sink potential. According to the assessment report released by the Intergovernmental Panel on Climate Change, 1ha of natural grassland can fix 1.3t of carbon per year, which is equivalent to reducing CO2 emissions by 6.9t. The soil carbon sink of forest and grassland ecosystems in Yunnan Province is relatively small. The soil carbon storage of forest and grassland in Yunnan is huge, which is 2.6 times the carbon storage of vegetation, and has the potential to increase carbon sink and fixation capacity. However, the soil carbon sink function of Yunnan ecosystem is currently weak (3.9 million tons of carbon / year), which is only equivalent to one-third of the vegetation carbon sink.

[0004] In summary, although grassland has a strong carbon sequestration capacity, it is also the ecosystem most seriously affected by human activities. Therefore, it is of great significance to adopt some grassland carbon management countermeasures, adapt to local conditions, and make use of harmful and poisonous weeds as resources and use their rapid decomposition and feedback methods to further enhance the grassland carbon sequestration capacity. Summary of the invention

[0005] The purpose of the present invention is to provide a method for promoting carbon sink by composting poisonous weeds, which can carry out composting treatment on poisonous weeds, realize resource utilization of poisonous weeds, reduce toxicity and increase soil carbon density at the collection site.

[0006] The embodiment of the present invention is achieved as follows:

[0007] A method for promoting carbon sequestration by composting poisonous weeds and feeding back, comprising:

[0008] Collect the poisonous weeds in the sample plot and crush them;

[0009] Treatment sites were excavated within the plots, and the excavated soil was mixed with nano-sized ferrihydrite to form a soil mixture;

[0010] The crushed poisonous weeds are laid at the treatment point to form a poisonous weed layer, the soil mixture is covered on the ground weed layer to form a soil layer, and multiple poisonous weed layers and multiple soil layers are alternately stacked to form a pile, and the top layer of the pile is the soil layer;

[0011] The pile is covered with a film for high-temperature composting, and then the film is removed and fermentation and composting continues under natural conditions; after composting is completed, the poisonous weed layer and the soil layer are mixed evenly and returned to the sample site.

[0012] The beneficial effects of the embodiments of the present invention are:

[0013] The embodiment of the present invention provides a method for promoting carbon sink by composting and feeding poisonous weeds, which includes collecting poisonous weeds in a sample plot, crushing poisonous weeds, establishing a processing point, mixing and adding nano-sized ferrihydrite, short-term high-temperature composting, natural composting, feeding back, etc., which can effectively reduce the toxicity of poisonous weeds, and accelerate the composting of poisonous weeds to feed back to the collection site, thereby improving the soil fertility of the collection site. In addition, the method of the present invention can reduce the carbon loss caused by the release of poisonous weeds in the form of CO2 during the degradation process, thereby significantly increasing the content of soil organic carbon. The method can effectively treat common poisonous weeds such as Rhus verniciflua, nettle, Alocasia odora, and Ambrosia trilobata, and has a better scope of application. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0015] The following is a detailed description of a method for promoting carbon sink by composting poisonous weeds according to an embodiment of the present invention.

[0016] A method for promoting carbon sequestration by composting poisonous weeds and feeding back, comprising:

[0017] S1. Collect the poisonous weeds in the sample plot and crush them;

[0018] S2. digging a treatment point in the sample plot, and mixing the excavated soil with nano-sized ferrihydrite to form a soil mixture;

[0019] S3. Laying crushed poisonous weeds at the treatment point to form a poisonous weed layer, covering the ground weed layer with a soil mixture to form a soil layer, and alternately stacking multiple poisonous weed layers and multiple soil layers to form a pile, the top layer of the pile being the soil layer;

[0020] S4. Cover the pile with a film for high-temperature composting, then remove the film and continue to ferment and compost under natural conditions; after composting is completed, mix the poisonous weed layer and the soil layer evenly and return them to the sample site.

[0021] Furthermore, the use of film covering can allow the temperature of the pile to reach 40-50°C within 3-5 days, and up to 60-70°C. Such high temperatures can effectively promote the degradation of toxins, thereby effectively weakening the toxicity of poisonous weeds. And under continuous high temperatures, some seeds of poisonous weeds will also be killed, thereby reducing the adverse effects of poisonous weeds on native plants. The time for high-temperature decomposition should not be too long. Continuous high temperatures for too long will kill the bacteria that are conducive to fermentation, thereby affecting the fermentation effect. The duration of high-temperature decomposition is 30-40 days, after which the film should be removed to allow the temperature of the pile to drop naturally, and continue to decompose under natural conditions for 120-150 days. Allow the organic matter in the poisonous weeds to be fully degraded. When judging whether the decomposition is complete, you can judge by observing indicators such as color, smell and temperature. Generally, as the composting time increases, the color of the pile gradually darkens to dark brown or black, the odor becomes lighter (the composting process will produce unpleasant gases such as hydrogen sulfide and nitric oxide, which are weaker or even disappear after composting), the particles are looser, and the temperature of the pile after composting is the same as or slightly higher than the ambient temperature (within 5°C) and will not change significantly.

[0022] Optionally, when collecting poisonous weeds, it is necessary to collect them in different areas; the area of ​​the collection area of ​​poisonous weeds in the same pile shall not exceed 30m 2 The types and properties of the poisonous weeds collected by the zones are relatively uniform, and the degree of fermentation can be better controlled during the composting and fermentation. Optionally, in actual operation, a circular area within a certain radius can be selected with a certain point as the center for collection, or a square area within a certain length and width range can be demarcated for collection. When selecting a square area, it should be noted that the length and width difference should not be too large.

[0023] The collected poisonous weeds are fully crushed to form fragments with a particle size of no more than 10mm. Sufficient crushing can destroy the cell structure of the poisonous weeds, so that the toxins are completely released and better degraded under high temperature. At the same time, the weed seeds can be destroyed during the crushing process, reducing the number of poisonous weeds.

[0024] Furthermore, the soil lumps with a diameter greater than 5 mm in the soil dug out from the treatment point are crushed and then mixed with nano-sized ferrihydrite. After such treatment, the soil and nano-sized ferrihydrite can be mixed more evenly, thereby better promoting the decomposition of poisonous weeds. Optionally, the soil dug out from the treatment point and the nano-sized ferrihydrite are mixed in a mass ratio of 1:0.02 to 0.03. Within this ratio range, the utilization efficiency of the nano-sized ferrihydrite is the highest, achieving a better decomposition effect at a lower cost, and at the same time will not affect the soil environment.

[0025] The nano-sized ferrihydrite used in the present invention has an average particle size of 30 to 80 nm, a purity of 99%, and a specific surface area of ​​35 to 40 m 2 / g, volume density is 0.72~0.75g / cm 3 The nano-sized ferrihydrite can not only promote the decomposition of poisonous weeds, but also effectively reduce the carbon loss in the form of CO2 during the degradation of poisonous weeds, thereby achieving the effect of carbon fixation.

[0026] When stacking, the thickness of the poisonous weed layer is 15 to 30 cm; the thickness of the soil layer is 3 to 8 cm. The number of poisonous weed layers and soil layers in the pile is 3 to 5 layers respectively. When stacking in this way, the poisonous weeds have a higher decomposition efficiency.

[0027] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0028] Example 1

[0029] This embodiment provides a method for promoting carbon sequestration by composting poisonous weeds, which comprises:

[0030] S1. Collect raw materials:

[0031] In the selected grassland sample plot, poisonous weeds are collected according to the number of poisonous weeds required for the pile. The collection process of poisonous weeds is divided into different areas to ensure that the poisonous weeds in a pile come from the same area. The area of ​​a poisonous weed collection plot is 5m×6m=30m 2 .

[0032] S2. Reduce the toxicity of poisonous weeds

[0033] The collected poisonous weed raw materials are fully crushed into pieces no larger than 10 mm, so that the structure of the poisonous weeds is destroyed, thereby reducing the toxicity and effectively reducing the number of poisonous weed seedlings.

[0034] S3. Heap point establishment:

[0035] A place with a certain slope was selected in the sample plot as the treatment point, and the soil was dug out on the spot, and the soil blocks with a size of more than 5 mm in the soil produced by the excavation pile were broken up.

[0036] S4. Adding nano-sized ferrihydrite:

[0037] The soil excavated from the treatment point is mixed with nano-sized ferrihydrite in a mass ratio of 1:0.02 and stirred evenly to form a soil mixture.

[0038] S5. Build the heap:

[0039] Divide the crushed poisonous weeds into five portions, put the first portion of poisonous weeds into the pile to form a dead poisonous weed layer with a thickness of about 25 cm, then evenly cover the poisonous weed layer with the soil mixture to form a soil layer with a thickness of about 5 cm, and tamp it down with your feet. Alternately stack five poisonous weed layers and five soil layers to form a pile, and finally cover the top layer with soil.

[0040] S6. Aging and ripening:

[0041] After the pile is formed, water is poured on the surface, and finally the entire pile is sealed with plastic film to achieve high-temperature decomposition conditions; in order to avoid high-temperature decomposition killing the bacteria that are conducive to fermentation, short-term high-temperature decomposition is adopted. After 30 days of decomposition, the plastic film is removed to allow the temperature to naturally drop to room temperature. The poisonous weeds in the pile continue to decompose under natural conditions for 120 to 150 days before completion, and the organic matter will be degraded and converted into various small molecules.

[0042] S7. Maturity test:

[0043] By observing the color, smell, temperature and other indicators of the poisonous weeds, we can further judge whether they have been completely decomposed. As the composting time increases, the color of the pile will generally gradually darken to dark brown or black, and the smell will become lighter. It will no longer have the decomposed smell at the beginning, and the particles will be looser. At the same time, the temperature of the pile after decomposition is the same as or slightly higher than the ambient temperature, and will not change significantly.

[0044] S7. Feedback:

[0045] After a period of composting and degradation, the poisonous weeds in the pile will decompose into various small molecular substances. Mixing the decomposed poisonous weeds in the pile with the soil mixture and stirring them evenly can form a carbon fixation additive, which can then be returned to the area where the raw materials are collected, thereby increasing the conversion rate of plant carbon to soil carbon and improving the soil carbon sequestration capacity of the area.

[0046] Example 2

[0047] This embodiment provides a method for promoting carbon sequestration by composting poisonous weeds, which comprises:

[0048] S1. Collect raw materials:

[0049] In the selected grassland sample plot, poisonous weeds are collected according to the number of poisonous weeds required for the pile. The collection process of poisonous weeds is divided into different areas to ensure that the poisonous weeds in a pile come from the same area. The area of ​​a poisonous weed collection plot is 5m×5m=25m 2 .

[0050] S2. Reduce the toxicity of poisonous weeds

[0051] The collected poisonous weed raw materials are fully crushed into pieces no larger than 10 mm, so that the structure of the poisonous weeds is destroyed, thereby reducing the toxicity and effectively reducing the number of poisonous weed seedlings.

[0052] S3. Heap point establishment:

[0053] A place with a certain slope was selected in the sample plot as the treatment point, and the soil was dug out on the spot, and the soil blocks with a size of more than 5 mm in the soil produced by the excavation pile were broken up.

[0054] S4. Adding nano-sized ferrihydrite:

[0055] The soil excavated from the treatment point is mixed with nano-sized ferrihydrite in a mass ratio of 1:0.02 and stirred evenly to form a soil mixture.

[0056] S5. Build the heap:

[0057] Divide the crushed poisonous weeds into five portions, put the first portion of poisonous weeds into the pile to form a dead poisonous weed layer with a thickness of about 15 cm, then evenly cover the poisonous weed layer with the soil mixture to form a soil layer with a thickness of about 3 cm, and tamp it down with your feet. Alternately stack five poisonous weed layers and five soil layers to form a pile, and finally cover the top layer with soil.

[0058] S6. Aging and ripening:

[0059] After the pile is formed, water is poured on the surface, and finally the entire pile is sealed with plastic film to achieve high-temperature decomposition conditions; in order to avoid high-temperature decomposition killing the bacteria that are conducive to fermentation, short-term high-temperature decomposition is adopted. After 40 days of decomposition, the plastic film is removed to allow the temperature to naturally drop to room temperature. The poisonous weeds in the pile continue to decompose under natural conditions for 120 to 150 days before completion, and the organic matter will be degraded and converted into various small molecules.

[0060] S7. Maturity test:

[0061] By observing the color, smell, temperature and other indicators of the poisonous weeds, we can further judge whether they have been completely decomposed. As the composting time increases, the color of the pile will generally gradually darken to dark brown or black, and the smell will become lighter. It will no longer have the decomposed smell at the beginning, and the particles will be looser. At the same time, the temperature of the pile after decomposition is the same as or slightly higher than the ambient temperature, and will not change significantly.

[0062] S7. Feedback:

[0063] After a period of composting and degradation, the poisonous weeds in the pile will decompose into various small molecular substances. Mixing the decomposed poisonous weeds in the pile with the soil mixture and stirring them evenly can form a carbon fixation additive, which can then be returned to the area where the raw materials are collected, thereby increasing the conversion rate of plant carbon to soil carbon and improving the soil carbon sequestration capacity of the area.

[0064] Example 3

[0065] This embodiment provides a method for promoting carbon sequestration by composting poisonous weeds, which comprises:

[0066] S1. Collect raw materials:

[0067] In the selected grassland sample plot, poisonous weeds are collected according to the number of poisonous weeds required for the pile. The collection process of poisonous weeds is divided into different areas to ensure that the poisonous weeds in a pile come from the same area. The collection plot of a poisonous weed is a circular area with a radius of 3 cm, and the area = 28.26m 2 .

[0068] S2. Reduce the toxicity of poisonous weeds

[0069] The collected poisonous weed raw materials are fully crushed into pieces no larger than 10 mm, so that the structure of the poisonous weeds is destroyed, thereby reducing the toxicity and effectively reducing the number of poisonous weed seedlings.

[0070] S3. Heap point establishment:

[0071] A place with a certain slope was selected in the sample plot as the treatment point, and the soil was dug out on the spot, and the soil blocks with a size of more than 5 mm in the soil produced by the excavation pile were broken up.

[0072] S4. Adding nano-sized ferrihydrite:

[0073] The soil excavated from the treatment point is mixed with nano-sized ferrihydrite in a mass ratio of 1:0.02 and stirred evenly to form a soil mixture.

[0074] S5. Build the heap:

[0075] Divide the crushed poisonous weeds into four parts, put the first part of the poisonous weeds into the pile to form a dead poisonous weed layer with a thickness of about 30cm, then evenly cover the poisonous weed layer with the soil mixture to form a soil layer with a thickness of about 8cm, and tamp it down with your feet. Alternately stack four poisonous weed layers and four soil layers to form a pile, and finally cover the top layer with soil.

[0076] S6. Aging and ripening:

[0077] After the pile is formed, water is poured on the surface, and finally the entire pile is sealed with plastic film to achieve high-temperature decomposition conditions; in order to avoid high-temperature decomposition killing the bacteria that are conducive to fermentation, short-term high-temperature decomposition is adopted. After 35 days of decomposition, the plastic film is removed to allow the temperature to naturally drop to room temperature. The poisonous weeds in the pile continue to decompose under natural conditions for 120 to 150 days before completion, and the organic matter will be degraded and converted into various small molecules.

[0078] S7. Maturity test:

[0079] By observing the color, smell, temperature and other indicators of the poisonous weeds, we can further judge whether they have been completely decomposed. As the composting time increases, the color of the pile will generally gradually darken to dark brown or black, and the smell will become lighter. It will no longer have the decomposed smell at the beginning, and the particles will be looser. At the same time, the temperature of the pile after decomposition is the same as or slightly higher than the ambient temperature, and will not change significantly.

[0080] S7. Feedback:

[0081] After a period of composting and degradation, the poisonous weeds in the pile will decompose into various small molecular substances. Mixing the decomposed poisonous weeds in the pile with the soil mixture and stirring them evenly can form a carbon fixation additive, which can then be returned to the area where the raw materials are collected, thereby increasing the conversion rate of plant carbon to soil carbon and improving the soil carbon sequestration capacity of the area.

[0082] Comparative Example 1

[0083] This comparative example provides a method for promoting carbon sequestration by composting poisonous weeds, which is basically the same as the method in Example 1, except that nano-sized ferrihydrite is not used, and the excavated soil is directly used for pile construction.

[0084] Comparative Example 2

[0085] This comparative example provides a method for promoting carbon sequestration by composting poisonous weeds, which is basically the same as the method in Example 1, except that the high-temperature composting step is eliminated, the pile is not covered with a film, and the compost is directly decomposed under natural conditions for 150 to 180 days.

[0086] Comparative Example 3

[0087] This comparative example provides a method for promoting carbon sequestration by composting poisonous weeds, which is basically the same as the method in Example 1, except that the high-temperature composting time is extended to 60 days.

[0088] Comparative Example 4

[0089] This comparative example provides a method for promoting carbon sequestration by composting poisonous weeds, which is basically the same as the method in Example 1, except that step S2 is omitted and the poisonous weeds are not crushed.

[0090] Comparative Example 5

[0091] This comparative example provides a method for promoting carbon sequestration by composting poisonous weeds, which is basically the same as the method in Example 1, except that when collecting the poisonous weeds, the weeds are not collected by partition, but the poisonous weeds in multiple partitions are mixed and collected.

[0092] Comparative Example 6

[0093] This comparative example provides a method for promoting carbon sequestration by composting poisonous weeds, which is basically the same as the method in Example 1, except that when stacking, the poisonous weeds are not stacked in layers, but all stacked at the bottom and the soil mixture is all laid on the top.

[0094] Test example

[0095] The methods of Examples 1 to 3 and Comparative Examples 1 to 6 were used to treat the sample plots respectively, and the carbon increase of each sample plot was statistically analyzed. The results are shown in Table 1.

[0096] Table 1. Statistics of carbon increase in various sites

[0097]

[0098] As can be seen from Table 1, the toxicity of poisonous weeds is significantly weakened by the methods of Examples 1 to 3 of the present invention. The median lethal dose of about 560 to 585 mg / kg is increased to 3025 to 3128 mg / kg. At the same time, the organic carbon loss of poisonous weeds is 36% to 40%, and the organic carbon loss is significantly reduced. The conversion rate of vegetation carbon to soil carbon is 25% to 30%. One year after the finished product is returned to the forest after being decomposed, the soil organic carbon in the area increases by 20% to 24%. This shows that the method has a significant carbon-enhancing effect.

[0099] In contrast, in Comparative Example 1, the use of nano-ferrihydrite was eliminated, and it can be seen that the organic carbon loss was as high as 69%, and the organic carbon loss was obvious. The conversion rate of vegetation carbon to soil carbon was 7.8%. One year after the finished product was returned to the forest after decomposition, the soil organic carbon in the area increased by 6.3%. A large amount of organic carbon was emitted in the form of CO2, and the carbon increase effect could not be achieved.

[0100] In Comparative Example 2, high temperature decomposition was cancelled, and the median lethal dose of the poisonous weeds of about 590 mg / kg was only increased to 1050 mg / kg. Although the toxicity was still weakened to a certain extent, the effect was significantly worse. In addition, without high temperature decomposition, the organic carbon loss rate of the poisonous weeds increased to a certain extent, and the carbon increase efficiency was significantly affected.

[0101] In Comparative Example 3, the high temperature composting time was extended, and the toxicity reduction effect of poisonous weeds was improved to a certain extent, but the organic carbon loss rate of poisonous weeds increased to 52%, the vegetation carbon to soil carbon conversion rate decreased to 17%, and the soil organic carbon increment was only 10%. Continuous high temperature for too long killed the fermentation microorganisms, which significantly affected the fermentation efficiency.

[0102] In Comparative Example 4, the poisonous weeds were not crushed, and the toxicity weakening effect of the poisonous weeds was reduced. At the same time, the carbon enhancement effect was also affected to a certain extent. It can be seen that crushing the poisonous weeds is conducive to the release of toxins, thereby achieving a better effect of reducing toxicity.

[0103] In Comparative Example 5, poisonous weeds from multiple zones were collected together without partitioning. Due to the large differences in the types and properties of poisonous weeds in each zone, there were obvious differences in the maturity of the poisonous weeds, resulting in a significant reduction in the carbon enrichment effect.

[0104] Comparative Example 6 was not stacked in layers during the decomposition process. After 150 to 180 days of decomposition, the decomposition effect was uneven, with the poisonous weeds at the top completely decomposed and the poisonous weeds at the bottom decomposed slowly, resulting in an increase in organic carbon loss to 58% and an increase in soil organic carbon of only 7.9%.

[0105] In summary, the embodiment of the present invention provides a method for promoting carbon sink by composting and feeding poisonous weeds, which includes collecting poisonous weeds in a sample plot, crushing poisonous weeds, establishing a processing point, mixing and adding nano-hydrite, short-term high-temperature composting, natural composting, feeding back, etc., which can effectively reduce the toxicity of poisonous weeds, and accelerate the composting of poisonous weeds to feed back to the collection site, thereby improving the soil fertility of the collection site. In addition, the method of the present invention can reduce the carbon loss caused by the release of poisonous weeds in the form of CO2 during the degradation process, thereby significantly increasing the content of soil organic carbon. The method can effectively treat common poisonous weeds such as Rhus verniciflua, nettle, Alocasia odora, and Ambrosia trilobata, and has a better scope of application.

[0106] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for promoting carbon sink by composting poisonous weeds, characterized in that: include: Collect the poisonous weeds in the sample plot and crush them; digging a treatment point in the sample plot, and mixing the excavated soil with nano-sized ferrihydrite to form a soil mixture; Laying crushed poisonous weeds at the treatment point to form a poisonous weed layer, covering the soil mixture on the ground weed layer to form a soil layer, and alternately stacking a plurality of the poisonous weed layers and a plurality of the soil layers to form a pile, wherein the top layer of the pile is the soil layer; The pile is covered with a film for high temperature composting, and then the film is removed and the composting is continued under natural conditions; after the composting is completed, the poisonous weed layer and the soil layer are evenly mixed and returned to the sample site.

2. The method according to claim 1, characterized in that: The time for high-temperature composting is 30 to 40 days, and the time for composting under natural conditions after removing the film is 120 to 150 days.

3. The method according to claim 1, characterized in that When collecting the poisonous weeds, they need to be collected in different areas; the area of ​​the collection area of ​​the poisonous weeds in the same pile shall not exceed 30m 2 .

4. The method according to claim 1, characterized in that: The collected poisonous weeds are fully crushed to form fragments with a particle size not greater than 10 mm.

5. The method according to claim 1, characterized in that The soil lumps with a diameter greater than 5 mm in the soil excavated from the treatment point are crushed and then mixed with the nano-sized ferrihydrite.

6. The method according to claim 5, characterized in that The average particle size of the nano-sized ferrihydrite is 30 to 80 nm, and the specific surface area is 35 to 40 m 2 / g, volume density is 0.72~0.75g / cm 3 .

7. The method according to claim 6, characterized in that The soil excavated from the treatment point and the nano-sized ferrihydrite are mixed in a mass ratio of 1:0.02-0.

03.

8. The method according to claim 1, characterized in that The thickness of the poisonous weed layer is 15 to 30 cm; the thickness of the soil layer is 3 to 8 cm.

9. The method according to claim 8, characterized in that The number of the poisonous weed layer and the soil layer in the pile body is 3 to 5 layers respectively.

10. The method according to claim 1, characterized in that When the color of the pile turns into dark brown, there is no obvious odor, the particles are loose, and the temperature does not exceed the ambient temperature by 5°C, the composting is complete.

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