Material for accelerating degradation of soil mulching film plastic and increasing organic carbon in soil and application of material

Abstract

The invention belongs to the field of plastic degradation, and particularly relates to a material for accelerating soil mulching film plastic degradation and improving soil organic carbon and application. The material is a carbon-based fertilizer or a composite material of the carbon-based fertilizer and zero-valent iron. The preparation process of the carbon-based fertilizer comprises the following steps: mixing chicken manure, straw and a conditioner charcoal according to a mass ratio of (1.2-2): 1: (0.3-0.5), and carrying out aerobic composting to obtain the carbon-based fertilizer; the preparation process of the composite material of the carbon-based fertilizer and the zero-valent iron comprises the following steps: adding the zero-valent iron into the carbon-based fertilizer, and uniformly mixing, wherein the mass ratio of the carbon-based fertilizer to the zero-valent iron is 3: (4-6). The method has the beneficial effects that the plastic sample of a pure soil system is aged and degraded, and the risk of soil organic carbon loss exists while the plastic sample in the soil environment is aged and degraded; the carbon-based fertilizer or the material obtained by co-adding the carbon-based fertilizer and zero-valent iron can promote aging and degradation of plastic of the soil mulching film and has the effect of soil carbon sequestration at the same time.

Description

Technical Field

[0001] The present invention belongs to the field of plastic degradation, and specifically relates to a material and its application for accelerating the degradation of plastic mulch in soil and enhancing soil organic carbon. Background Art

[0002] China is a large agricultural country with a very high proportion of farmland in all land resources. In farmland soil, plastic products are widely used and in large quantities. While enjoying the convenience of plastic products, environmental pollution caused by the difficulty of traditional plastic products to degrade follows. Biodegradable plastics have entered the public eye due to their good mechanical properties, processing properties, biocompatibility and other advantages. Currently, they are mainly applied to agricultural mulch films, fertilizer and pesticide packaging, plastic greenhouses and other aspects. Research shows that biodegradable plastics are more likely to form smaller microplastics compared to other plastics, and have a more significant impact on the agricultural ecosystem. It is worth noting that the concentration of microplastics in the soil environment is 4 - 23 times that in the water environment, and biodegradable plastics in the soil have various impacts on the soil, including both physical and chemical property changes and biological impacts. These changes may have a profound impact on the health and function of the soil ecosystem, so further research is needed to evaluate its ecological safety and long-term effects.

[0003] Currently, research mainly focuses on the species analysis and concentration monitoring of traditional plastics in the soil, and there are still many deficiencies in research in other fields. For example, regarding the research on emerging biodegradable plastics, the exploration is significantly insufficient, the research types are relatively single, and the long-term environmental behavior in in-situ soil still needs to be further explored. The Chinese patent application with the publication number CN115651664A and the invention name of a method for reducing greenhouse gas emissions from plastic-polluted soil while simultaneously improving plastic degradation efficiency and soil nutrients discloses straw and / or biochar materials for degrading polyethylene films. The polyethylene film is a traditional plastic, and the annual degradation rate of the plastic in this patent is at most about 6%, with limited degradation efficiency and a risk of soil organic carbon loss in this patent. Summary of the Invention

[0004] The purpose of the present invention is to provide a material and its application for accelerating the degradation of plastic mulch in soil and enhancing soil organic carbon.

[0005] To achieve the above objective, the technical solution adopted by the present invention is as follows: A material for accelerating the degradation of plastic mulch in soil and enhancing soil organic carbon, which is a carbon-based fertilizer or a composite material of carbon-based fertilizer and zero-valent iron;

[0006] The preparation process of the carbon-based fertilizer is: Mix chicken manure, straw and conditioning agent biochar for aerobic composting, where the mass ratio of chicken manure, straw and biochar is (1.2 - 2):1:(0.3 - 0.5) to obtain the carbon-based fertilizer;

[0007] The preparation process of the composite material of carbon-based fertilizer and zero-valent iron is as follows: Add zero-valent iron to the carbon-based fertilizer and mix evenly. The mass ratio of the carbon-based fertilizer to zero-valent iron is 3:4 to 6.

[0008] Furthermore, the soil mulch film is a biodegradable plastic with an addition amount not exceeding 6%, and the addition amount refers to the mass percentage of the biodegradable plastic to the soil.

[0009] In the present invention, the addition amount of the soil mulch film is relatively large, and the maximum addition amount can reach 6%. It can be seen that the carbon-based fertilizer and the composite material of the carbon-based fertilizer and zero-valent iron in the present invention have excellent degradation performance for plastics.

[0010] When preparing the organic fertilizer, chicken manure and straw are mixed and then aerobic composting is carried out for 28 to 32 days to obtain the organic fertilizer; during the composting period, it is regularly turned over. At the end of the composting, the pH is 6 to 10, the EC is 0 to 5 ms / cm, and the DOC content is 0 to 30 g / kg.

[0011] Among them, a conditioner biochar is added at the beginning of the aerobic composting of chicken manure and straw, and it is carried out for 28 to 32 days to obtain the carbon-based fertilizer; during the composting period, it is regularly turned over. At the end of the composting, the pH is 6 to 10, the EC is 0 to 5 ms / cm, and the DOC content is 0 to 10 g / kg.

[0012] The soil mulch film described above is a biodegradable plastic BDP or biodegradable plastic mulch films with different degradation degrees.

[0013] Another object of the present invention is to provide a preparation method of the material for accelerating the degradation of the soil mulch film plastic and enhancing the soil organic carbon as described above.

[0014] Another object of the present invention is to disclose the application of the material for accelerating the degradation of the soil mulch film plastic and enhancing the soil organic carbon. The mixture is added to the soil with a soil mulch film, where the soil mulch film is a biodegradable plastic with an addition amount not exceeding 6%.

[0015] Furthermore, the application ratio of the carbon-based fertilizer in the soil is 2.5 to 4 wt% (referring to the mass percentage of the carbon-based fertilizer to the soil. When actually applied to farmland soil, the soil refers to the surface soil evenly mixed with the carbon-based fertilizer, usually with a thickness of 5 to 20 cm), and the application ratio of zero-valent iron in the soil is 4 to 6 wt% (referring to the mass percentage of zero-valent iron to the soil. When actually applied to farmland soil, the soil refers to the surface soil evenly mixed with zero-valent iron, usually with a thickness of 5 to 20 cm). For the composite material of the carbon-based fertilizer and zero-valent iron, the carbon-based fertilizer and zero-valent iron are compounded in proportion and then evenly mixed with the surface soil.

[0016] The application ratio of the carbon-based fertilizer should not be lower than 2.5 wt%, otherwise it will reduce the degradation efficiency of soil mulch plastics and affect soil carbon sequestration. The application ratio of zero-valent iron in the soil is 4-6 wt%. Combining with the fertilization ratio of the carbon-based fertilizer, within this ratio range, the materials obtained by co-adding the carbon-based fertilizer and zero-valent iron can achieve a better balance in promoting the aging degradation of soil mulch plastics and soil carbon sequestration.

[0017] In a preferred embodiment, the soil mulch and the materials for accelerating the degradation of soil mulch plastics and enhancing soil organic carbon are uniformly mixed and then added to the soil at one time.

[0018] Among them, the applicable soil parameters are: pH 6.5-9, EC is between 300-1500 μs / cm, and the moisture content of the air-dried soil is 1.5%-3%.

[0019] Among them, enhancing soil organic carbon means increasing the content of soil SOC. Accelerating the degradation of soil mulch plastics means increasing the film degradation rate, oxygen element content and carbon-oxygen index COI.

[0020] The beneficial effect of the present invention is that the plastic samples in the pure soil system have undergone aging degradation, and there is a risk of loss of soil organic carbon during the aging degradation of plastic samples in the soil environment. However, the materials obtained by co-adding the carbon-based fertilizer or the carbon-based fertilizer and zero-valent iron can have the effect of soil carbon sequestration while promoting the aging degradation of soil mulch plastics. Description of the Drawings

[0021] Figure 1 It is the scanning electron microscope image of biodegradable plastic BDP with different treatments in the application example of the present invention;

[0022] Figure 2 It is the comparison chart of the change of the carbon-oxygen index COI of biodegradable plastic BDP with different treatments in the first year in the application example of the present invention;

[0023] Figure 3 It is the comparison chart of the change of soil organic carbon SOC with different treatments in the application example of the present invention;

[0024] Figure 4 It is the comparison chart of the change of soil dissolved organic carbon DOC in the first year with different treatments in the application example of the present invention;

[0025] Figure 5 It is the comparison chart of the change of the three-dimensional fluorescence regional integration FRI of soil dissolved organic matter DOM in the first year with different treatments in the application example of the present invention. Detailed Embodiments

[0026] The present invention will be specifically introduced below in conjunction with the drawings and specific embodiments.

[0027] Example 1 Preparation of Materials for Accelerating the Degradation of Soil Mulch Plastics and Enhancing Soil Organic Carbon

[0028] Preparation of organic fertilizer: 5.4 kg of chicken manure (from Musen Fertilizer Industry) and 3.6 kg of wheat straw (purchased from Huifeng Straw Agricultural Products Deep Processing Company) were mixed for aerobic composting. The final moisture was controlled at about 60%, and it was maintained for 30 days. During this period, turning the pile was carried out every 5 days to obtain the organic fertilizer. When the aerobic composting ended, the pH was 8.0, the EC was 3.39 ms / cm, and the DOC content was 25.10 g / kg;

[0029] Preparation of carbon-based fertilizer: 5.4 kg of chicken manure (from Musen Fertilizer Industry) and 3.6 kg of wheat straw (purchased from Huifeng Straw Agricultural Products Deep Processing Company) were mixed, and 1.5 kg of conditioning biochar (purchased from Zhejiang Runsheng New Energy Co., Ltd., with cedar as the raw material, prepared under the condition of 4000) was added at the beginning of the aerobic composting of chicken manure and straw. The pH of the biochar was 7.82, the C content was 67.59%, the N content was 1.01%, the H content was 4.42%, and the S content was 0.09%. Aerobic composting was carried out, and the final moisture was controlled at about 60%, and it was maintained for 30 days. During this period, turning the pile was carried out every 5 days. When the aerobic composting ended, the pH was 8.8, the EC was 2.90 ms / cm, and the DOC content was 9.50 g / kg.

[0030] Preparation of the composite material of carbon-based fertilizer and zero-valent iron: The carbon-based fertilizer prepared above was mixed with zero-valent iron (where the mass ratio of carbon-based fertilizer to zero-valent iron was 3:5, and the zero-valent iron ZVI was purchased from Guangzhou Metal Metallurgy (Group) Co., Ltd.) to form the composite material of carbon-based fertilizer and zero-valent iron.

[0031] Application example

[0032] In this experiment, biodegradable plastics, organic fertilizers, carbon-based fertilizers, and zero-valent iron were designed to be added to the soil in Nanjing area. During the experiment, 5 g of plastic and 100 g of mixed soil (the original soil had a pH of 7.54, an EC of 347.87 μs / cm, a water content of 18%, and the mixed soil was formed after adding organic fertilizer, carbon-based fertilizer, and / or zero-valent iron to the original soil) were used as a culture system and cultured in an incubator. The addition methods of 3 wt% of organic fertilizer (3 wt% refers to the mass ratio of organic fertilizer to soil), 3 wt% of carbon-based fertilizer (3 wt% refers to the mass ratio of carbon-based fertilizer to soil), and 5 wt% of zero-valent iron (5 wt% refers to the mass ratio of zero-valent iron to soil) were to uniformly mix them with the original soil according to the application ratio and then load them into the incubator. Three replicate samples were set for each treatment, and they were cultured at a constant temperature of 25 °C for two years. Sampling and extraction of plastics and soil were carried out at 12 months (Y1) and 24 months (Y2) respectively.

[0033] The biodegradable plastic bag BDP (PE + ore biological enzyme degradation plastic masterbatch) was purchased from Jinhua Limei Packaging Materials Co., Ltd. Before the experiment, the biodegradable plastic bag BDP was cut into plastic fragments of 2×2 cm, and the plastic fragments were evenly distributed in the soil. The cut plastic sheets were vortexed in 75% ethanol (100 sheets / 20 ml) for 5 min. After pouring out the ethanol, the same volume of clean ethanol was added, and this operation was repeated three times. After fishing out, it was thoroughly washed with ultrapure water and air-dried naturally at room temperature for 48 h for use. The organic fertilizer added was the organic fertilizer obtained in Example 1, the carbon-based fertilizer was the carbon-based fertilizer obtained in Example 1, and the composite material of the added carbon-based fertilizer and zero-valent iron was the composite material of the carbon-based fertilizer and zero-valent iron obtained in Example 1.

[0034] Four experimental treatments were set in this experiment: CK (soil), OF (soil added with 3 wt% organic fertilizer), BOF (soil added with 3 w% carbon-based fertilizer), BOF-ZVI (soil added with 3 wt% carbon-based fertilizer and 5 wt% zero-valent iron); Nanjing area (118.87E, 32.03N); Two-year dynamic sampling was carried out; There were 3 parallels, a total of 24 treatment groups.

[0035] During the soil cultivation process, samples were taken at 12 months (Y1) and 24 months (Y2) for detection. First, the biodegradable plastic fragments were separated from the soil samples with tweezers, and washed with ultrapure water many times until there was no obvious soil sample on the surface. After air-drying, they were randomly selected and packaged for subsequent characterization. Subsequently, the collected soil samples were air-dried and placed in a light-proof environment for soil physical and chemical property tests.

[0036] For the biodegradable plastic, the method of random selection was adopted, and 3 - 15 pieces were packaged for characterization. The weighing method was used to calculate its mass loss, so as to obtain the degradation rate of the biodegradable plastic BDP. The results are shown in Table 1. Randomly select some biodegradable plastics for EDS energy spectrum scanning to determine the element types and contents on the surface of the biodegradable plastic. The oxygen element content on the surface of the biodegradable plastic obtained at the scale of 2 μ spectrum is shown in Table 2. Randomly select some biodegradable plastics for scanning electron microscope testing at the scale of 5 shown. Figure 1 As shown. The surface functional groups of some randomly selected biodegradable plastics were determined by Fourier transform infrared spectroscopy (FTIR), and the resolution was 4 cm -1 For each sample, 32 scans were carried out in the range of 400 - 4000 cm -1 Subsequently, the carbon-oxygen index COI in the first year was calculated, and the results are as Figure 2 shown. Weigh the air-dried soil samples, digest the soil samples using the digestion method, and subsequently determine the content of soil organic carbon SOC in the soil samples by ultraviolet spectrophotometry. The results are as Figure 3As shown, a certain amount of air-dried soil sample was weighed, the dissolved organic matter (DOM) in the soil was extracted, and the content of dissolved organic carbon (DOC) was measured. The results are as Figure 4 shown. The three-dimensional fluorescence spectrum scanning test was carried out on the extracted soil dissolved organic matter (DOM), and the subsequent regional integration (FRI) analysis was carried out to obtain the content changes of the absolute volume of each region. The results are as Figure 5 shown.

[0037] The change of the degradation rate (calculated by mass loss) of biodegradable plastic (BDP) in Nanjing area is shown in Table 1.

[0038] Table 1 Degradation rate (calculated by mass loss) of biodegradable plastic (BDP) in Nanjing area

[0039] Y1 Y2 CK 46.43％ 45.54％ OF 47.32％ 48.21％ BOF 52.68％ 58.04％ BOF-ZVI 60.71％ 63.39％

[0040] It can be seen from Table 1 that the degradation rates of BDP in the organic fertilizer (OF) group and the soil control (CK) group are relatively close. Compared with the soil CK group, the degradation rate of the OF group increased by 0.89% in the first year and 2.67% in the second year; the biochar-based organic fertilizer (BOF) group can promote the degradation of biodegradable plastic (BDP) in the soil, increasing the degradation rate by 6.25% in the first year and 12.5% in the second year. The addition of the mixed material BOF-ZVI significantly increased the degradation rate of biodegradable plastic (BDP) in the soil environment, increasing by 14.28% and 17.85% in the first and second years respectively.

[0041] The change of the oxygen element content of biodegradable plastic (BDP) in Nanjing area is shown in Table 2.

[0042] Table 2 Oxygen element content of biodegradable plastic (BDP) in Nanjing area (2μm)

[0043] Y1 Y2 CK 11.7％ 17.4％ OF 13.7％ 21.4％ BOF 16.4％ 21.9％ BOF-ZVI 36.7％ 35.3％

[0044] It can be seen from Table 2 that the addition of organic fertilizer (OF) and biochar-based organic fertilizer (BOF) increased the oxygen content on the plastic surface, that is, both of them can promote the degradation of biodegradable plastic (BDP) in the soil from the perspective of oxygen content, increasing the oxygen content by 2.0% and 4.7% respectively in the first year and 4.0% and 4.5% respectively in the second year. The addition of the mixed material BOF-ZVI significantly increased the oxygen content on the surface of biodegradable plastic (BDP) in the soil environment, increasing by 25.0% and 17.9% respectively in the first and second years, greatly promoting the aging degradation of biodegradable plastic (BDP) in the soil environment.

[0045] As Figure 1As shown, according to the results of scanning electron microscopy, the addition of organic fertilizer OF and biochar-based fertilizer BOF caused obvious protrusions and tears on the plastic surface, which can prove that organic fertilizer OF and biochar-based fertilizer BOF can promote the aging of biodegradable plastic BDP in the soil environment. The addition of the mixed material BOF-ZVI made the protrusions and tears on the surface of biodegradable plastic BDP in the soil environment larger and more obvious, indicating that the addition of BOF-ZVI further promoted the aging and degradation of biodegradable plastic BDP in the soil environment.

[0046] As Figure 2 shown, it can be seen from the change of the carbon-oxygen index COI in the first year that biodegradable plastic BDP degraded in the soil environment. Compared with the original plastic sample, the carbon-oxygen index COI of the CK group increased, the C-O content increased, and C-H was broken. After the addition of organic fertilizer OF, it was close to the carbon-oxygen index COI of the CK group. Compared with the CK group, the carbon-oxygen index COI of the organic fertilizer OF group in the first year increased by 0.39%. The addition of biochar-based fertilizer BOF increased the carbon-oxygen index COI of the plastic and promoted the degradation of biodegradable plastic BDP in the soil. Compared with the CK group, the carbon-oxygen index COI of the biochar-based fertilizer BOF group in the first year increased by 12.87%. The addition of the mixed material BOF-ZVI significantly increased the carbon-oxygen index COI of biodegradable plastic BDP in the soil environment, increasing by 22.43% in the first year, further promoting the aging and degradation of biodegradable plastic BDP in the soil environment.

[0047] As Figure 3 shown, the addition of organic fertilizer OF and biochar-based fertilizer BOF increased the soil SOC content, increasing the soil organic carbon content SOC by 59.17% and 195.15% respectively in the first year, and increasing the soil organic carbon content SOC by 41.16% and 138.83% respectively in the second year. The addition of the mixed material BOF-ZVI increased the soil organic carbon content SOC by 112.85% and 78.85% respectively in the first year and the second year compared with the CK group, showing a good carbon sequestration effect. The addition of the mixed material significantly increased the soil organic carbon content SOC and reduced the risk of soil organic carbon loss during plastic degradation in the soil environment. The biochar-based fertilizer BOF group obtained a higher proportion of soil organic carbon content SOC increase, while its plastic degradation rate was lower than that of the BOF-ZVI group.

[0048] As Figure 4 shown, taking the first year as an example, the addition of organic fertilizer OF and biochar-based fertilizer BOF increased the soil dissolved organic carbon DOC content, increasing the soil dissolved organic carbon DOC content by 95.99% and 87.75% respectively in the first year; the addition of the mixed material BOF-ZVI increased the soil dissolved organic carbon DOC content by 97.2% in the first year compared with the CK group. It can be seen that the addition of biochar-based fertilizer and mixed material significantly increased the soil dissolved organic carbon and reduced the risk of total soil carbon loss during plastic degradation in the soil environment.

[0049] As Figure 5 shown, taking the first year as an example, the addition of organic fertilizer OF and biochar-based organic fertilizer BOF increased the content of humic acid-like substances in Region V. In the first year, the content of humic acid-like substances was increased by 92.41% and 72.94% respectively. The addition of the mixed material BOF-ZVI increased the content of humic acid-like substances in the first year by 89.11% compared with the CK group. It can be seen that the addition of organic fertilizer, biochar-based organic fertilizer, and mixed material significantly increased the content of humic acid-like substances, improved the degree of soil humification, and enhanced soil fertility, but the plastic degradation rate in the organic fertilizer group did not increase significantly. Among them, I is tyrosine of aromatic protein; II is tryptophan of aromatic protein; III is fulvic acid of aromatic; IV is soluble microbial by-product-like; V is humic acid-like.

[0050] The above embodiments are only used to illustrate the technical solutions of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form. Any technical solutions obtained by using equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A material for accelerating the degradation of soil mulch plastic and increasing soil organic carbon, characterized in that: The material is a carbon-based fertilizer or a composite material of a carbon-based fertilizer and zero-valent iron; The preparation process of the carbon-based fertilizer is as follows: chicken manure, straw and conditioner biochar are mixed for aerobic composting, wherein the mass ratio of chicken manure, straw and biochar is (1.2-2):1:(0.3-0.5), to obtain the carbon-based fertilizer; The preparation process of the composite material of carbon-based fertilizer and zero-valent iron is as follows: adding zero-valent iron to the carbon-based fertilizer and mixing evenly, and the mass ratio of the carbon-based fertilizer to the zero-valent iron is 3:4-6.

2. The material for accelerating the degradation of soil mulch plastic and increasing soil organic carbon according to claim 1, characterized in that: Soil mulch is biodegradable plastic with an added amount not exceeding 6%, and the added amount refers to the mass percentage of biodegradable plastic to soil.

3. The material for accelerating the degradation of soil mulch plastic and increasing soil organic carbon according to claim 1, characterized in that: At the beginning of aerobic composting of chicken manure and straw, biochar is added as a conditioner and maintained for 28 to 32 days to obtain charcoal-based fertilizer; the compost is turned regularly during the composting period. At the end of the composting, the pH is 6 to 10, the EC is 0 to 5ms / cm, and the DOC content is 0 to 10g / kg.

4. The material for accelerating the degradation of soil mulch plastic and increasing soil organic carbon according to claim 1, characterized in that: The soil mulch film is biodegradable plastic BDP or biodegradable plastic mulch films with different degradation degrees.

5. A method for preparing a material for accelerating the degradation of soil film plastic and increasing soil organic carbon as described in any one of claims 1 to 4.

6. An application of a material for accelerating the degradation of soil mulch plastic and increasing soil organic carbon, characterized in that: The material of any one of claims 1 to 4 is added to soil having a soil mulch, wherein the soil mulch is a biodegradable plastic with an addition amount of no more than 6%.

7. The use according to claim 6, characterized in that: The application ratio of carbon-based fertilizer in the soil is 2.5-4wt%, and the application ratio of zero-valent iron in the soil is 4-6wt%.

8. The use according to claim 6, characterized in that: The soil mulch and the material for accelerating the degradation of soil mulch plastic and increasing soil organic carbon are mixed well and added to the soil at one time.

9. The use according to claim 6, characterized in that: Soil parameters: pH 6.5-9, EC between 300 and 1500 μs / cm, and moisture content of air-dried soil between 1.5% and 3%.

10. The use according to claim 6, characterized in that: Improving soil organic carbon refers to increasing the soil SOC content; accelerating the degradation of soil mulch plastic refers to increasing the mulch degradation rate, oxygen content and carbon-oxygen index COI.

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