A method to reduce microplastic accumulation and migration in bamboo forest ecosystems
By applying biochar and Bacillus inoculant to Lei bamboo forests, combined with physical control and bioremediation methods, the problem of microplastic accumulation and migration in Lei bamboo forests was solved, achieving effective management of microplastics and ensuring soil health and the quality and safety of bamboo shoots.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- RES INST OF SUBTROPICAL FORESTRY CHINESE ACAD OF FORESTRY
- Filing Date
- 2026-05-07
- Publication Date
- 2026-07-31
AI Technical Summary
Existing technologies lack effective means to manage microplastic accumulation and migration in bamboo forest ecosystems. Especially under intensive management conditions, the risk of microplastic pollution is high, threatening soil health and food safety.
A combination of biochar and Bacillus inoculant was used. Biochar adsorbed and immobilized microplastics through its high specific surface area, while Bacillus degraded the microplastics. This combination of physical control and bioremediation methods inhibited the migration and accumulation of microplastics in the underground rhizomes of Phyllostachys edulis.
It effectively reduces the risk of microplastic migration and accumulation in the soil of Lei bamboo forest, maintains soil health, and ensures the quality and safety of bamboo shoots. It is low-cost, highly efficient, and sustainable.
Smart Images
Figure CN122477880A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of forestry ecological restoration technology, specifically relating to a method for reducing the accumulation and migration of microplastics in a bamboo forest ecosystem. Background Technology
[0002] Lei bamboo (Phyllostachys violascens) is an important bamboo species in my country for its shoots, characterized by rapid forest growth, early shoot emergence, high yield, and excellent quality, making it widely used in the construction of high-efficiency economic forests. Lei bamboo shoots, due to their high fiber, low fat, and rich amino acid content, are considered a green and healthy food with extremely high market value. To improve yield and economic benefits, current Lei bamboo forest management often employs intensive measures such as forest cover for warming and moisture retention, and the application of organic or chemical fertilizers. While these measures significantly promote earlier shoot emergence, increase yield, and improve quality, they also bring new environmental problems.
[0003] Under intensive management conditions, the Lei bamboo forest ecosystem inevitably faces frequent use and contact with plastic products, leading to a significant increase in the risk of microplastic (MPs, <5mm) residue and accumulation. Studies have shown that the main sources of MPs pollution in Lei bamboo forests include... Figure 1 As shown, the pollution includes: (1) pollution from covering materials and organic fertilizers: materials commonly used in bamboo shoot production, such as rice husks, straw, sawdust, and organic fertilizers, are easily exposed to plastic products during processing, transportation, and application. The MP particles released after the plastics decompose are then introduced into the soil. (2) pollution from chemical fertilizers: chemical fertilizers are easily exposed to plastic particles during packaging, storage, transportation, and application, becoming an important pathway for MP input. (3) external input: surrounding industries, transportation, human activities, sewage discharge, wastewater irrigation, and atmospheric deposition may all accelerate the migration of MPs into the bamboo forest ecosystem.
[0004] It is evident that intensively managed bamboo forests pose a serious risk of MPs pollution, which not only threatens soil health but also enters the food chain through root absorption and bioaccumulation during bamboo shoot development, thereby affecting food safety and human health. Current technologies lack effective and systematic solutions for addressing MPs pollution in bamboo forests, particularly under bamboo cover management conditions, where there is a lack of technical means that can simultaneously achieve pollution reduction, quality preservation, and eco-friendliness.
[0005] Therefore, there is an urgent need to develop an environmentally friendly technology and model that can effectively reduce the accumulation and migration of MPs in bamboo forest ecosystems, so as to ensure the safe production and ecological function of bamboo forests and provide scalable technical support for the control of plastic pollution in agriculture and forestry. Summary of the Invention
[0006] The purpose of this invention is to address the difficulty in effectively controlling the accumulation and migration of microplastics in intensively managed bamboo forest ecosystems, and to provide an environmentally friendly, low-cost, and highly operable comprehensive method for the control of microplastic pollution. The specific technical solution is as follows: A method for reducing microplastic accumulation and migration in a bamboo forest ecosystem, the method comprising the following steps: Apply biochar to the topsoil of the bamboo forest in the target area. The application rate is 50g per kilogram of soil biochar. After application, mix the biochar evenly with the soil and let it stand for 7 days.
[0007] Bacillus inoculant was applied to the soil surface of the target area of the Leizhu forest at a concentration of 2×10⁻⁶. 8 The dosage is 5 mL per kilogram of soil, applied once every 30 days, for a total of 3 applications.
[0008] During the above application treatment, maintain the soil moisture content at 70% to 90% of field capacity.
[0009] By combining the adsorption and fixation of microplastics by biochar with the degradation of microplastics by Bacillus, the migration and accumulation of soil microplastics in the underground rhizomes of Phyllostachys edulis can be inhibited.
[0010] Furthermore, the biochar is corn stalk biochar, which is produced by pyrolysis and carbonization of corn stalks at 500 to 600°C under oxygen-limited conditions.
[0011] Furthermore, before covering the bamboo forest with biochar, a fertilization trench with a depth of 5 to 10 cm is dug along the direction of the bamboo rhizome extension, and the biochar is mixed evenly with the topsoil and applied. After backfilling and compaction, water is poured to ensure that the biochar is in full contact with the soil and microplastics.
[0012] Furthermore, the Bacillus inoculant is applied by root irrigation, with an irrigation depth of not less than 10 cm; the three application times are day 0, day 30 and day 60 after biochar application; before application, the bacterial solution is diluted with water at a volume ratio of 1:5 and then applied, and the application time is selected when the temperature is below 25℃.
[0013] The polymer types of the microplastics include one or more of polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polystyrene (PS), polyethylene (PE), acrylonitrile-butadiene-styrene copolymer (ABS), and polymethyl methacrylate (PMMA), and the microplastic particle size ranges from 20 to 5000 μm.
[0014] Furthermore, the method also includes a step of quantitatively assessing the degree of microplastic pollution in the target area before remediation treatment. This quantitative assessment employs the Pollution Load Index (PLI) model and the Ecological Risk Index (H) model, with the specific steps as follows: Calculate the type of microplastic polymer at each sampling point pollution coefficient : In the formula, For the first in the soil Measured abundance of microplastics of various polymer types (number / kg dry soil). As a reference background value, the baseline value of microplastic abundance (cells / kg dry soil) in soil of the same type of bamboo forest that has not been disturbed by intensive management was taken.
[0015] Calculate each sampling point Comprehensive pollution load index of polymer types : In the formula, This represents the total number of polymer types detected.
[0016] Calculate the polymer types Single ecological risk factor : In the formula, For the first The toxicity response factors for microplastics of various polymer types were determined, with the following values: ABS=6552, PE=11, PVC=10001, PS=30, PP=1, PET=4, PMMA=1021; a comprehensive ecological risk index was calculated. : .
[0017] The method for collecting soil samples required for the quantitative assessment is as follows: set up no less than 3 5m×5m quadrats in the target bamboo forest, collect mixed soil samples in three layers: 0–10cm, 10–20cm, and 20–40cm, with no less than 6 replicates in each layer, and calculate the abundance of each polymer type after identification by flotation-filtration-microscopy combined with Raman spectroscopy (excitation wavelength 532nm), and substitute them into the model for assessment.
[0018] Furthermore, the quantitative assessment was conducted at three time points: before the repair treatment (day 0), during the repair process (day 45), and after the repair treatment (day 90). PLI and H values were calculated for each assessment and compared with the previous results. When the PLI value of the same point decreases by no less than 20% in two consecutive assessments and the ecological risk index H level decreases by at least one level, it is determined that the restoration treatment has initially achieved the expected results.
[0019] Furthermore, classify and rate the pollution risks according to PLI and H; classify PLI < 1, 1 ≤ PLI < 2, and 2 ≤ PLI as Class I, Class II, and Class III, respectively, corresponding to mild pollution, moderate pollution, and severe pollution; classify H ≤ 10, 10 < H < 100, 100 ≤ H < 1000, and H ≥ 1000 as Grade I, Grade II, Grade III, and Grade IV, respectively, corresponding to low risk, medium risk, relatively high risk, and high risk; When the evaluation results on the 90th day meet the requirements that PLI is reduced by at least one category and H is reduced by at least one grade, it is determined that the remediation effect is good, and enter the maintenance management stage. Adjust the annual supplementary application amount of biochar to 20 g per kilogram of soil and extend the application cycle of Bacillus agents to once a year; Otherwise, supplement the application of biochar to 20 g per kilogram of soil, shorten the application cycle of Bacillus agents to once every 20 days, and re-evaluate after another complete treatment cycle.
[0020] Furthermore, the specific implementation measures for maintaining the soil moisture content at 70% to 90% of the field capacity include: In the target Moso bamboo forest, bury one soil moisture sensor (accuracy ±1% v / v) in each of the soil layers of 5–10 cm and 15–20 cm at a distance of 30 cm from the direction of bamboo rhizome extension, and automatically record the volumetric water content once every 24 hours.
[0021] Before treatment, use the cutting ring method (100 cm³) to measure the field capacity of each sample plot , which serves as the calculation reference value for the irrigation amount; when the sensor monitors that the soil volumetric water content is lower than ×70%, start water replenishment, and use a drip irrigation system (drip head spacing 30–40 cm, rated flow 1.5–2.0 L / h) arranged along the direction of the bamboo rhizome. The single irrigation amount (L / m²): ; In the formula, is the currently measured volumetric water content (cm³ / cm³); is the planned wetting depth, taking 0.3 m; is the irrigation water use coefficient, taking 0.9.
[0022] Furthermore, when the water content exceeds ×90% due to rainfall, suspend irrigation and check the drainage ditch for smoothness to prevent the runoff from carrying microplastics to migrate and spread.
[0023] When the daily maximum temperature exceeds 30°C, adjust the irrigation time to early morning (06:00–08:00) or evening (18:00–20:00) to reduce evaporation loss and maintain the activity of Bacillus.
[0024] The assessment of the remediation effect also includes evaluating the adsorption and interception effect of the underground rhizome system of *Phyllostachys nigra* on microplastics using the bioaccumulation factor (BAF). The bioaccumulation factor is calculated using the following formula: In the formula, The abundance of microplastics in bamboo rhizomes or rhizome tissue (numbers / g dry weight). The corresponding abundance of microplastics in rhizosphere soil (number of microplastics / g dry weight).
[0025] The evaluation criteria for the repair effect are as follows: when the BAF in the bamboo rhizome decreased by more than 30% compared with the control group (CK) and the BAF in the rhizome root decreased by more than 25%, the biocontrol effect was deemed to be significant; when the microplastic abundance in the bamboo shoots (collected when they are about 30cm from the ground) decreased by more than 40% compared with the control group after the treatment, the quality and safety of the bamboo shoots were deemed to have been effectively improved.
[0026] Furthermore, the method also includes the following soil environmental maintenance measures during the treatment cycle: soil pH is measured every 30 days; if pH < 5.5, limestone powder (CaCO3, purity ≥ 95%) is applied at 200–300 g / m² 7 days before the application of Bacillus inoculant to adjust the pH to 6.0–7.0 to maintain the optimal survival environment for Bacillus; if pH > 7.5, sulfur powder (20–30 g / m²) can be applied to adjust the pH; during the first application of Bacillus inoculant, 5 mL / kg soil is applied simultaneously with humic acid water-soluble fertilizer (humic acid content ≥ 50 g / L) to provide carbon source substrate and promote colonization of the inoculant; during the treatment period, the input of new plastic products during mulching operations should be reduced, and when mulching is necessary, biodegradable mulching materials (such as bamboo powder-based biodegradable mulch film) should be preferred to reduce the continuous input of exogenous microplastics; During the treatment period, the application of chemical fungicides that inhibit Bacillus (such as difenoconazole, carbendazim, etc.) is prohibited. If disease control is necessary, biological pesticides should be selected, and the application of inoculants should only be resumed 15 days after the last application. During the treatment period, compound fertilizer (N:P:K=15:15:15) should be applied at a rate of 300 mg N / kg soil, divided into 3 applications with irrigation water to avoid affecting the growth of bamboo seedlings and the development of rhizomes due to insufficient nutrition, which would affect the accuracy of the microplastic control effect assessment.
[0027] The method is applicable to covered bamboo forests where the microplastic pollution level assessment results are PLI≥1 and H≥10.
[0028] Compared with the prior art, the beneficial effects of this invention are: This invention comprehensively utilizes physical barrier control and bioremediation methods. It introduces the high specific surface area adsorption capacity of biochar and the plastic degradation function of specific microorganisms, using an appropriate concentration of biochar (50 g / kg) and a low dose of microbial agent (50 ml / 10 kg ± 2 × 10⁻⁶). 8The CFU / mL concentration can effectively reduce the absorption and accumulation of MPs by bamboo components, achieving synergistic management of MPs in the soil of covered bamboo forests. This invention establishes a comprehensive management strategy for MPs pollution in covered bamboo forests, characterized by low cost, high efficiency, and sustainability. It not only effectively reduces the risk of MP migration and accumulation in the soil but also helps maintain the health and ecological function of bamboo forest soil, thereby ensuring the quality and safety of bamboo shoots and the sustainable use of forest land. Attached Figure Description
[0029] Figure 1 This is a schematic diagram illustrating the sources of MPs pollution in bamboo forests according to the present invention. Figure 2 The distribution of plastics (A) and the speciation of MPs (B) in the soil of the intensively managed Leizhu bamboo forest of the present invention; Figure 3 The present invention relates to the soil MPs polymer type (A) and MPs abundance (B) of different soil layers in the intensive management of Leizhu bamboo forests. Figure 4 The abundance (a) and enrichment factor (b) of MPs in each component of the intensively managed Lei bamboo forest of the present invention. Figure 5 This is a diagram showing the occurrence characteristics of MPs in the underground rhizomes and bamboo shoots of the intensively managed Leizhu bamboo forest according to the present invention. Figure 6 This is a diagram showing the effect of the biochar and microbial inoculants of the present invention on the abundance of total MPs in the rhizomes. Figure 7 This diagram illustrates the effect of biochar and microbial inoculants of the present invention on the abundance of PP in the rhizomes. Detailed Implementation
[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of this invention, not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0031] A method for reducing microplastic accumulation and migration in a bamboo forest ecosystem, the method comprising the following steps: Apply biochar to the topsoil of the bamboo forest in the target area. The application rate is 50g per kilogram of soil biochar. After application, mix the biochar evenly with the soil and let it stand for 7 days.
[0032] Bacillus inoculant was applied to the surface soil of the target area of the Leizhu bamboo forest at a concentration of 2×10⁻⁶. 8 The dosage is 5 mL per kilogram of soil, applied once every 30 days, for a total of 3 applications.
[0033] During the above application treatment, maintain the soil moisture content at 70% to 90% of field capacity.
[0034] By combining the adsorption and fixation of microplastics by biochar with the degradation of microplastics by Bacillus, the migration and accumulation of soil microplastics in the underground rhizomes of Phyllostachys edulis can be inhibited.
[0035] The biochar is corn stalk biochar, which is produced by pyrolysis and carbonization of corn stalks at 500 to 600°C under limited oxygen conditions.
[0036] Before covering the bamboo forest with biochar, a fertilization trench 5 to 10 cm deep is dug along the direction of the bamboo rhizome extension, and the biochar is mixed evenly with the topsoil and applied. After backfilling and compaction, water is poured to ensure that the biochar is in full contact with the soil and microplastics.
[0037] The Bacillus inoculant is applied by root irrigation, with an irrigation depth of not less than 10 cm. The three application times are day 0, day 30 and day 60 after biochar application. Before application, the inoculant solution is diluted with water at a volume ratio of 1:5 and then applied. The application time is selected when the temperature is below 25℃.
[0038] The polymer types of the microplastics include one or more of polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polystyrene (PS), polyethylene (PE), acrylonitrile-butadiene-styrene copolymer (ABS), and polymethyl methacrylate (PMMA), and the microplastic particle size ranges from 20 to 5000 μm.
[0039] The method further includes a step of quantitatively assessing the degree of microplastic pollution in the target area before remediation treatment. This quantitative assessment employs the Pollution Load Index (PLI) model and the Ecological Risk Index (H) model. The specific steps are as follows: Calculate the type of microplastic polymer at each sampling point pollution coefficient : In the formula, For the first in the soil Measured abundance of microplastics of various polymer types (number / kg dry soil). As a reference background value, the baseline value of microplastic abundance (cells / kg dry soil) in soil of the same type of bamboo forest that has not been disturbed by intensive management was taken.
[0040] Calculate each sampling point Comprehensive pollution load index of polymer types : In the formula, This represents the total number of polymer types detected.
[0041] Calculate the polymer types Single ecological risk factor : In the formula, For the first The toxicity response factors for microplastics of various polymer types were determined, with the following values: ABS=6552, PE=11, PVC=10001, PS=30, PP=1, PET=4, PMMA=1021; a comprehensive ecological risk index was calculated. : .
[0042] The method for collecting soil samples required for the quantitative assessment is as follows: set up no less than 3 5m×5m quadrats in the target bamboo forest, collect mixed soil samples in three layers: 0–10cm, 10–20cm, and 20–40cm, with no less than 6 replicates in each layer, and calculate the abundance of each polymer type after identification by flotation-filtration-microscopy combined with Raman spectroscopy (excitation wavelength 532nm), and substitute them into the model for assessment.
[0043] The quantitative assessment was conducted at three time points: before the repair treatment (day 0), during the repair treatment (day 45), and after the repair treatment (day 90). PLI and H values were calculated for each assessment and compared with the previous results. When the PLI value of the same point decreases by no less than 20% in two consecutive assessments and the ecological risk index H level decreases by at least one level, it is determined that the restoration treatment has initially achieved the expected results.
[0044] Pollution risk is classified and rated according to PLI and H; PLI<1, 1≤PLI<2, 2≤PLI<3, and PLI≥3 are classified into Class I, Class II, Class III, and Class IV, respectively, corresponding to clean, lightly polluted, moderately polluted, and heavily polluted; H<40, 40≤H<80, 80≤H<160, and H≥160 are rated into Level I, Level II, Level III, and Level IV, respectively, corresponding to low risk, medium risk, relatively high risk, and high risk. When the assessment results on the 90th day meet the criteria of PLI being reduced by at least one category and H being reduced by at least one level, the remediation effect is deemed to be good, and the maintenance management phase is entered. The annual biochar supplementation amount is adjusted to 20g per kilogram of soil, and the application cycle of Bacillus inoculant is extended to once a year. Otherwise, supplement with biochar up to 20g per kilogram of soil, shorten the application cycle of Bacillus inoculant to once every 20 days, and continue treatment for a full cycle before reassessing.
[0045] Specific implementation measures to maintain soil moisture content at 70% to 90% of field capacity include: Within the target bamboo forest, soil moisture sensors (accuracy ±1%v / v) were installed at 30cm from the direction of bamboo rhizome extension, at soil layers of 5–10cm and 15–20cm respectively, and the volumetric moisture content was automatically recorded every 24 hours.
[0046] Field water holding capacity of each plot was measured using the ring sampler method (100 cm³) before treatment. This serves as the baseline value for calculating irrigation volume; when the sensor detects that the soil volumetric moisture content is lower than... When the soil moisture reaches 70%, replenishment water should be initiated using a drip irrigation system laid along the direction of the bamboo rhizome (drip emitter spacing 30–40 cm, rated flow rate 1.5–2.0 L / h). The single irrigation volume... (L / m²): In the formula, This represents the current measured volumetric moisture content (cm³ / cm³). The planned wetting depth is 0.3m; The irrigation water utilization coefficient is taken as 0.9.
[0047] Rainfall caused the moisture content to exceed When the flow rate reaches 90%, suspend irrigation and check the drainage ditches for blockages to prevent runoff from carrying microplastics and causing them to migrate and spread.
[0048] When the daily maximum temperature exceeds 30°C, the irrigation time should be adjusted to early morning (06:00–08:00) or late evening (18:00–20:00) to reduce evaporation loss and maintain Bacillus activity.
[0049] The assessment of the remediation effect also includes evaluating the adsorption and interception effect of the underground rhizome system of *Phyllostachys nigra* on microplastics using the bioaccumulation factor (BAF). The bioaccumulation factor is calculated using the following formula: In the formula, The abundance of microplastics in bamboo rhizomes or rhizome tissue (numbers / g dry weight). The corresponding abundance of microplastics in rhizosphere soil (number of microplastics / g dry weight).
[0050] The evaluation criteria for the repair effect are as follows: when the BAF in the bamboo rhizome decreased by more than 30% compared with the control group (CK) and the BAF in the rhizome root decreased by more than 25%, the biocontrol effect was deemed to be significant; when the microplastic abundance in the bamboo shoots (collected when they are about 30cm from the ground) decreased by more than 40% compared with the control group after the treatment, the quality and safety of the bamboo shoots were deemed to have been effectively improved.
[0051] The method also includes the following soil environmental maintenance measures during the treatment cycle: soil pH is measured every 30 days; if pH < 5.5, limestone powder (CaCO3, purity ≥ 95%) is applied at 200–300 g / m² 7 days before the application of Bacillus inoculant to adjust the pH to 6.0–7.0 to maintain the optimal survival environment for Bacillus; if pH > 7.5, sulfur powder (20–30 g / m²) can be applied to adjust the pH; at the first application of Bacillus inoculant, 5 mL / kg soil is applied simultaneously with humic acid water-soluble fertilizer (humic acid content ≥ 50 g / L) to provide carbon source substrate and promote colonization of the inoculant; during the treatment period, the input of new plastic products during mulching operations should be reduced, and when mulching is necessary, biodegradable mulching materials (such as bamboo powder-based biodegradable mulch film) should be preferred to reduce the continuous input of exogenous microplastics; During the treatment period, the application of chemical fungicides that inhibit Bacillus (such as difenoconazole, carbendazim, etc.) is prohibited. If disease control is necessary, biological pesticides should be selected, and the application of inoculants should only be resumed 15 days after the last application. During the treatment period, compound fertilizer (N:P:K=15:15:15) should be applied at a rate of 300 mg N / kg soil, divided into 3 applications with irrigation water to avoid affecting the growth of bamboo seedlings and the development of rhizomes due to insufficient nutrition, which would affect the accuracy of the microplastic control effect assessment.
[0052] The method is applicable to covered bamboo forests where the microplastic pollution level assessment results are PLI≥1 and H≥10.
[0053] To verify the method and technical effects of the present invention, a major production area of Lei bamboo was selected as a typical representative sampling area. Within each sampling area, Lei bamboo forests covering the periphery of towns (residential areas) and the suburbs were selected according to different areas of human activity. Then, based on the differences in the management intensity of the Lei bamboo forests, Lei bamboo forests with different covering years (0, 2, 4 and 6 years) were selected. Six 10m×10m quadrats were set up in each Lei bamboo forest with a distance of more than 10m between the quadrats to investigate the bamboo forest structure.
[0054] Stratified soil samples (0-10, 10-20, 20-40 cm) were collected in each quadrat, mixed, and the abundance of soil MPs was determined. Six replicates were set for each sampling area.
[0055] Based on the soil MPs risk assessment results, different pollution levels (mild, moderate, and severe) of covered bamboo forests were selected. The potential ecological risks of MPs in the soil and bamboo shoots of covered bamboo forests were quantitatively assessed using the Pollution Load Index (PLI) model and the Hazard Index (H) model.
[0056] Based on the soil MPs risk assessment results, bamboo forests with different MPs pollution levels (mild, moderate, and severe) were selected for coverage. Bamboo shoots and other above-ground components as well as underground rhizomes were collected during three periods: May-June (peak growth period of underground rhizomes), August-September (bud differentiation period), and December-January of the following year (forest cover period).
[0057] Bamboo forest component samples were collected during three key periods (peak growth period of underground rhizomes in May-June, shoot differentiation period in August-September, and forest cover period in December-January of the following year). (1) Underground rhizomes: rhizomes and roots of 2-year-old bamboo and stump roots of 2-year-old bamboo were collected for MPs abundance analysis. (2) Bamboo shoots: bamboo shoots about 30cm above the ground were collected for MPs abundance analysis. Six biological replicates were set up for each type of sample to ensure the reliability of the data. Based on the measurement results, the bioaccumulation factors of MPs in stump roots, rhizomes, bamboo rhizomes and bamboo shoots were calculated.
[0058] Soil from intensively managed Lei bamboo forests was selected, and polypropylene (PP, density 1.38 g / cm³, particle size 40 μm, concentration 1 g / kg soil) was added as the target MPs.
[0059] According to the design, add the corresponding mass of PP granules to every 5 kg of soil, place it in a plant cultivation greenhouse for 3 months to balance, and maintain the soil moisture at 60%–80% of field capacity during this period.
[0060] After equilibration, the soil was air-dried, crushed, and sieved through a 2mm sieve. The experiment consisted of 7 treatment groups, including control (CK, PP only) and PP-R1, PP-R2, PP-R3, PP-B1, PP-B2, and PP-B3, with 10 pots per treatment and 1 replicate per pot.
[0061] Corn biochar was selected and applied one week after mixing with PP; Bacillus cells were collected by centrifugation after being cultured in LB liquid medium at 30°C and 150 rpm for 48 hours, and then resuspended in sterile water to prepare a bacterial suspension (concentration 2×10⁻⁶). 8 (CFU / mL), administered once a month for a total of 3 times starting from the start of the experiment. The specific design for each treatment group is shown in Table 1.
[0062] Table 1 Experimental Design of Biochar and Bacillus Treatment Seedling cultivation utilizes the mother bamboo rhizome propagation method, selecting robust one-year-old bamboo seedlings (approximately 2.5cm in diameter) from pollution-free Lei bamboo forests. A 25cm rhizome segment with buds is retained, and one seedling is planted per pot. Planting method: fill the pot with soil to 5cm below the bottom, lay the rhizome segment flat, cover with soil to 1cm from the rim, compact, and water thoroughly. Each pot contains approximately 10kg of soil. Potted seedlings are managed in a greenhouse. During the maintenance period, compound fertilizer (N:P:K = 15:15:15) is applied at a rate of 300mg N / kg soil, applied in three applications with irrigation water. Soil moisture is maintained at 70%–90% field capacity, and regular irrigation and weeding are carried out.
[0063] After 10 months of treatment, the rhizome system of *Phyllostachys edulis* was obtained, and the roots and rhizomes were separated for MPs abundance analysis and bioaccumulation factor calculation. The effects of biochar and microbial agents on the adsorption and degradation of major MPs were evaluated.
[0064] like Figure 2-3 As shown, plastic pollution is prevalent in intensively managed bamboo forests. Figure 2 A) These plastics gradually degrade into microplastics (MPs) through biological, physical, or chemical reactions. The pollution risk of MPs increases significantly with prolonged exposure to these microplastics. Studies have shown that MPs in the soil of *Phyllostachys edulis* forests mainly exist in fibrous, flaky, and granular forms. Figure 2 B), the main polymer types include PET, PS, PVC, PP, nylon (PA), acrylonitrile-butadiene-styrene copolymer (ABS) and PE ( Figure 3 A). With the increase in the number of years of intensive management of bamboo forests, the abundance of MPs in the soil showed a trend of first increasing and then decreasing. Figure 3 B).
[0065] Soils in *Phyllostachys edulis* forests at different management levels were generally at a moderate MPs pollution risk level (Class III). Some local areas showed higher potential ecological risks due to the accumulation of high-risk MPs, as shown in Table 2, indicating a significant enrichment trend of MPs in forest soils. The MPs pollution risk in soils of normally growing stands (HB) and severely degraded stands (DB) caused by intensive management was assessed using the Ecological Risk Index (H) and the Pollution Load Index (PLI). The H index was divided into levels I–IV, with higher levels indicating greater potential ecological risk. Numbers 0, 2, and 4 correspond to management levels of 0 years (no cover), 2–3 years (short-term cover), and 4–6 years (long-term cover), respectively (the same applies below).
[0066] Table 2. Assessment of MPs Pollution Risk Level in Soil of Intensively Managed Leizhu Forests like Figure 4As shown, under the same cover management conditions, the abundance of MPs in the "rhizome-shoot" system of naturally growing stands was significantly lower than that of degraded stands, with the difference reaching 2 times under cover conditions. This indicates that intensive management exacerbates the risk of MPs migration from the soil to the bamboo components. Figure 4 a).
[0067] Different operating years have a significant impact on the accumulation characteristics of MPs in various organs. Figure 4 a) In naturally growing forest stands, MPs are mainly enriched in rhizomes and stumps, and under long-term cover conditions, they further transfer to and enrich in bamboo shoots; while in degraded forest stands, stumps are always the main enrichment site, and bamboo shoots have a significantly weaker enrichment capacity.
[0068] The enrichment factor results show that ( Figure 4 (b) Degraded forest stands have a stronger overall enrichment capacity than naturally growing forest stands, but this capacity decreases with the extension of cover management years. In contrast, the enrichment capacity of various organs in naturally growing forest stands changes dynamically, ultimately leading to significant enrichment of MPs in bamboo shoots.
[0069] like Figure 5-7 As shown, in soils of *Phyllostachys edulis* forests at different management levels, MPs with a particle size smaller than 200 μm can be enriched by underground organs such as rhizomes, stumps, and mature rhizomes, with particles smaller than 50 μm being the predominant type. The main polymer types include PVC, PET, PP, and ACR, etc. Figure 5 Some MPs have been detected migrating into bamboo shoots.
[0070] Overall, under intensive management conditions, soil MPs in bamboo forests are prone to migration and are transported to the bamboo components through the root system. Among them, bamboo shoots, as the main edible part, show significant enrichment, which seriously affects the quality and food safety of bamboo shoots.
[0071] The application of biochar and microbial inoculants significantly regulates the enrichment level of MPs in the underground rhizome system. Figure 6 and Figure 7 Overall, both types of control measures can reduce the accumulation of MPs in the flagellate system under appropriate application intensities, but different application gradients exhibit differentiated response characteristics.
[0072] With increasing biochar application concentration, the abundance of total MPs in bamboo rhizomes and roots exhibited a "V"-shaped trend. The R2 treatment showed the lowest total MP concentration, significantly lower than treatments R1 and R3. The MP abundance in bamboo rhizomes under the R1 treatment was significantly higher than the control (CK), indicating that low-dose biochar may promote MP retention in the rhizome-root system by altering soil pore structure or surface adsorption sites. When the application concentration reaches the R2 level (50 g / kg), biochar may effectively reduce the migration and input of MPs into the underground system by enhancing soil aggregate stability and physical retardation, thereby inhibiting their accumulation.
[0073] Microbial inoculant treatment also showed a concentration-dependent response. With increasing application rate, the total MP concentration in bamboo rhizomes gradually increased, while the concentration in roots showed an inverted "V" shape. Both reached their lowest values under treatment B1, and were significantly lower than those under treatment CK. The high-dose treatment (B3) did not show a further reduction effect, suggesting that excessive inoculant may alter soil microstructure or organic matter degradation processes, affecting the migration behavior of MPs.
[0074] In the analysis of polypropylene (PP) components, treatments B1 and B2 significantly reduced PP accumulation in bamboo rhizomes; the PP concentration in the roots showed an inverted "V"-shaped change with increasing fungicide application rate, reaching its lowest level under treatment B3. Figure 7 This result indicates that different polymer types respond differently to regulatory measures, which may be related to microbial oxidative modification of the PP surface or remodeling of aggregate structures.
[0075] Comprehensive analysis shows that treatment with appropriate concentrations of biochar (R2, 50 g / kg) and low doses of microbial inoculant (B1, 50 mL / 10 kg soil) is most effective in inhibiting the accumulation of MPs in the rhizosphere system. This is comparable to the optimal application rate described in this invention (50 g / kg biochar, 5 mL / kg soil, concentration 2 × 10⁻⁶). 8 The CFU / mL ratio is consistent with the actual values, verifying the effectiveness of the technical solution of this invention.
[0076] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for reducing the accumulation and migration of microplastics in a bamboo forest ecosystem, characterized in that, The method includes the following steps: Apply biochar to the surface soil of the moso bamboo forest in the target area at a dosage of 50 g of biochar per kilogram of soil. After application, mix the biochar evenly with the soil and let it stand for 7 days. Bacillus inoculant was applied to the soil surface of the aforementioned bamboo forest at a concentration of 2 × 10⁻⁶. 8 The concentration of CFU / mL is 5 mL per kilogram of soil, applied once every 30 days, for a total of 3 applications. During the above application treatment, maintain the soil moisture content at 70% to 90% of the field capacity. Through the dual effects of the adsorption and fixation of microplastics by biochar and the degradation of microplastics by Bacillus, inhibit the migration and enrichment of soil microplastics to the underground rhizome root system of moso bamboo.
2. The method according to claim 1, characterized in that, The biochar is corn straw biochar, which is prepared by pyrolyzing and carbonizing corn straw under oxygen-limited conditions at 500 to 600 °C. Before the moso bamboo forest mulching operation, dig a fertilization trench with a depth of 5 to 10 cm along the direction of bamboo rhizome extension, then mix it evenly with the surface soil and apply it. After backfilling and compaction, water it to make the biochar fully contact with the soil and microplastics.
3. The method according to claim 2, characterized in that, The Bacillus agent is applied by root irrigation, and the irrigation depth is not less than 10 cm. The three application times are the 0th day, the 30th day, and the 60th day after the biochar is applied. Before application, dilute the bacterial solution with water at a volume ratio of 1:5 and then irrigate it. The application time is selected during the period when the temperature is lower than 25 °C.
4. The method according to claim 3, characterized in that, The polymer types of the microplastics include one or more of polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polystyrene (PS), polyethylene (PE), acrylonitrile-butadiene-styrene copolymer (ABS), and polymethyl methacrylate (PMMA), etc.
5. The method according to claim 4, characterized in that, The particle size range of the microplastics is 20 to 5000 μm.
6. The method according to claim 5, characterized in that, The method also includes the step of quantitatively evaluating the degree of microplastic pollution in the target area before the remediation treatment. The quantitative evaluation uses the pollution load index PLI model and the ecological risk index H model. The specific steps are as follows: Calculate the type of microplastic polymer at each sampling point pollution coefficient : In the formula, For the first in the soil Measured abundance of microplastics of various polymer types; For reference background values, the baseline values of soil microplastic abundance in similar bamboo forests that have not been disturbed by intensive management were taken; Calculate each sampling point Comprehensive pollution load index of polymer types : In the formula, This represents the total number of polymer types detected. Calculate each polymer type Single ecological risk factor : In the formula, For the first Toxicity response factors of microplastics of various polymer types; Calculate the comprehensive ecological risk index : .
7. The method according to claim 6, characterized in that, The method for collecting soil samples required for the quantitative evaluation is: set at least 3 5 m × 5 m quadrats in the target moso bamboo forest, collect soil mixed samples in three layers of 0–10 cm, 10–20 cm, and 20–40 cm, with at least 6 replicates for each layer. After flotation–filtration–microscope combined with Raman spectroscopy identification, calculate the abundance of each polymer type and substitute it into the model for evaluation.
8. The method according to claim 7, characterized in that, Classify and rate the pollution risks according to PLI and H; classify PLI < 1, 1 ≤ PLI < 2, 2 ≤ PLI as class I, class II, and class III respectively; corresponding to slight pollution, moderate pollution, and severe pollution respectively; classify H ≤ 10, 10 < H < 100, 100 ≤ H < 1000, H ≥ 1000 as grade I, grade II, grade III, and grade IV respectively; corresponding to low risk, medium risk, relatively high risk, and high risk respectively. When the evaluation result on the 90th day meets the requirement that PLI is reduced by at least one class and H is reduced by at least one grade, it is determined that the remediation effect is good, and enter the maintenance management stage. Adjust the annual supplementary application amount of biochar to 20 g per kilogram of soil and extend the application cycle of the Bacillus agent to once a year. Otherwise, supplement the application of biochar to 20 g per kilogram of soil, shorten the application cycle of the Bacillus agent to once every 20 days, and re-evaluate after another complete treatment cycle.
9. The method according to claim 1, characterized in that, Specific implementation measures to maintain soil moisture content at 70% to 90% of field capacity include: Within the target bamboo forest, soil moisture sensors were installed at 30cm from the direction of bamboo rhizome extension, at soil layers of 5–10cm and 15–20cm respectively, and the volumetric moisture content was automatically recorded every 24 hours. Field water holding capacity of each plot was determined using the ring sampler method before treatment. This serves as the baseline value for calculating irrigation volume; when the sensor detects that the soil volumetric moisture content is lower than... Replenishment water is initiated when the soil moisture reaches 70%, using a drip irrigation system laid along the direction of the bamboo rhizomes. The single irrigation volume... : In the formula, This represents the current measured volumetric moisture content (cm³ / cm³). The planned wetting depth is 0.3m; The irrigation water utilization coefficient is taken as 0.
9.
10. The method according to any one of claims 1 to 9, characterized in that, The method is applicable to covered bamboo forests where the microplastic pollution level assessment results are PLI≥1 and H≥10.