Soil microplastic migration inhibition method

Abstract

The invention relates to the technical field of soil new pollutant treatment, in particular to a soil microplastic migration inhibition method. Comprising the following steps: sampling soil at different depths, and determining the abundance of micro-plastics and soil texture; according to the method, different soil characteristics are determined through sampling analysis, soil conditioners with different formulas and mixing amounts are adopted, soil micro-plastic migration is inhibited in a targeted mode, hematite and gibbsite are used as raw materials, micro-plastic is stabilized through electrostatic attraction, gibbsite is used for auxiliary strengthening, unnecessary addition of weak migration soil is avoided, cost and resources are saved, and the method is suitable for industrial production. The original micro-plastic stabilization effect evaluation method is constructed, reliable standards and scientific bases are provided for evaluating and optimizing soil micro-plastic migration inhibition, the treatment efficiency and quality are improved, in addition, the abundance of the soil micro-plastic is quantitatively analyzed firstly, the material dosage is determined according to the soil condition, blind adding is avoided, and the method is suitable for large-scale popularization and application. The effective migration inhibition of the soil micro-plastics is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of new soil pollutant treatment, and in particular to a method for inhibiting the migration of soil microplastics. Background Art

[0002] Scientific discoveries in recent years have shown that new pollutants such as microplastics and PFAS are common in soil. Taking microplastic pollution as an example, it can migrate in the soil environment and enter the root system of crops or groundwater aquifers, thus posing a major threat to food security and drinking water safety. At present, there have been many explorations on the migration and fate of microplastics in soil, but there is still a large technical gap in the risk control of microplastics in the soil environment.

[0003] In response to this situation, this application proposes a method for inhibiting the migration of soil microplastics. First, the mobility of microplastics is evaluated based on the ratio of the abundance of microplastics in deep and shallow soils, and a quantitative relationship for material addition is constructed. By adding a conditioning agent of corresponding dosage and composition to the surface soil, the mobility of soil microplastics is reduced through adsorption, aggregation and sedimentation, thereby achieving effective control of the risk of soil microplastic pollution. Summary of the invention

[0004] The purpose of the present invention is to propose a method for inhibiting the migration of soil microplastics in view of the fact that there is still a large technical gap in the risk control of microplastics in the soil environment in the background technology.

[0005] The technical solution of the present invention is a method for inhibiting the migration of soil microplastics, comprising the following steps:

[0006] Sampling soil at different depths and determining microplastic abundance and soil texture;

[0007] Determine the formula and dosage of soil conditioner according to soil characteristics and prepare soil conditioner;

[0008] The soil conditioner is added to the soil at a specific depth and water is added to adjust the soil moisture content, and the treated soil is maintained;

[0009] The stabilization effect of soil microplastics was evaluated through soil leaching experiments, and the stabilization rate of soil microplastics was obtained.

[0010] Optionally, sampling soil at different depths and determining microplastic abundance and soil texture comprises the following steps:

[0011] The shallow soil at a depth of 0-10 cm and the deep soil at a depth of 40-60 cm were sampled by a soil sampler;

[0012] Microplastic characterization techniques, including infrared spectroscopy and laser confocal microscopy, were used to obtain the abundance of soil microplastics at two depths, recorded as [MP] 浅层 , [MP] 深层 ;

[0013] The ratio of the abundance of microplastics in deep and shallow soil is calculated as [MP] 深层 / [MP] 浅层 , and at the same time analyze the soil texture at a depth of 0-10cm to obtain the clay + silt content.

[0014] Optionally, the formula and dosage determination method of the soil conditioner include:

[0015] Soil clay + silt content ≤ 30% and [MP] 深层 / [MP] 浅层 ≤10%, choose only hematite as the formula, add 1-5g soil conditioner to 100g soil;

[0016] Soil clay + silt content ≤ 30% and [MP] 深层 / [MP] 浅层 >10%, choose only hematite as the formula, add 5-10g soil conditioner to 100g soil;

[0017] Soil clay + silt content> 30% and [MP] 深层 / [MP] 浅层 ≤10%, select 70-90% hematite + 10-30% gibbsite as the formula, add 1-5g soil conditioner to 100g soil;

[0018] Soil clay + silt content> 30% and [MP] 深层 / [MP] 浅层 >10%, select 70-90% hematite + 10-30% gibbsite as the formula, and add 5-10g soil conditioner to 100g soil.

[0019] Optionally, the method for preparing the soil conditioner includes selecting 150-200 mesh hematite and 150-200 mesh gibbsite as raw materials, and mixing the two according to a determined formula ratio.

[0020] Optionally, the mixing is performed by a ball mill, the ball milling speed is 200-300 rpm, and the ball milling time is 1-2 h.

[0021] Optionally, after adding the prepared soil conditioner to the soil at a depth of 0-20 cm, water is added to make the soil reach a saturated moisture content of 50-70%, and the treated soil is cured for 3-7 days.

[0022] Optionally, the soil leaching experiment comprises the following steps:

[0023] Take 8-12g of soil before adding materials and after adding materials and curing, respectively, and place them in a Buchner funnel, with a filter membrane placed at the bottom;

[0024] Use 0.5-1.5L ultrapure water to leach the soil, collect the leachate, analyze the abundance c of microplastics in the leachate, compare the abundance with the abundance c0 of the original soil leachate, and obtain the stabilization rate η, the formula is as follows:

[0025]

[0026] Optionally, the filter membrane is a stainless steel filter membrane with a pore size of 5-20 μm.

[0027] In summary, the present application includes at least one of the following beneficial technical effects:

[0028] 1. The present invention obtains the abundance of soil microplastics at different depths and the texture of shallow soil by sampling and analyzing the actual environmental soil, and then determines the formula and dosage of the soil conditioner according to the soil characteristics. For different clay and silt contents and different ratios of microplastic abundance in deep and shallow soils, different proportions of hematite and gibbsite formulas and different dosage ranges are used respectively. Since soils with high clay and silt contents are more likely to produce cracks under natural conditions, which serve as preferential channels for the migration of microplastics, a larger dosage is adopted for soils with higher clay and silt contents, so that the soil microplastic migration inhibition method is highly targeted, can meet the needs of different soil types to the greatest extent, and effectively improve the effect of inhibiting soil microplastic migration;

[0029] 2. The present invention uses hematite and gibbsite as raw materials for soil conditioners. Hematite and gibbsite are positively charged, while soil microplastics are negatively charged. The stabilization of microplastics is achieved by electrostatic attraction. Among them, gibbsite has stronger positive charge and can better adsorb negatively charged soil microplastics, which plays an auxiliary and reinforcing role in stabilization. For weakly mobile soils, there is no need to add gibbsite, which avoids unnecessary costs and waste of resources;

[0030] 3. The present invention constructs an original microplastic stabilization effect evaluation method, which provides a reliable standard for evaluating the soil microplastic migration inhibition effect, can accurately measure the effect of soil conditioners, and provides a scientific basis for optimizing the soil microplastic migration inhibition method. Through this evaluation method, the formula and dosage of soil conditioners can be adjusted in time to ensure that the soil microplastic migration inhibition effect reaches the best state and improve the efficiency and quality of governance;

[0031] 4. In the risk control of soil microplastics, the present invention first conducts a quantitative analysis of the abundance of microplastics in the soil at different depths, and then reasonably determines the dosage of materials that need to be added. This method of determining the material dosage based on the specific conditions of the soil avoids the waste of resources or poor treatment effects that may be caused by blindly adding materials. Through scientific quantitative analysis, it can ensure that the dosage of the added soil conditioner can achieve the maximum inhibition of the migration of soil microplastics.

[0032] The present invention determines different soil characteristics through sampling and analysis, adopts soil conditioners with different formulas and dosages to specifically inhibit the migration of soil microplastics, and uses hematite and gibbsite as raw materials, utilizes electrostatic attraction to stabilize microplastics, and gibbsite as auxiliary reinforcement to avoid unnecessary addition to weakly mobile soils, saving costs and resources. The present invention constructs an original microplastic stabilization effect evaluation method, which provides reliable standards and scientific basis for evaluating and optimizing the inhibition of soil microplastic migration, and improves the efficiency and quality of governance. In addition, the present invention first quantitatively analyzes the abundance of soil microplastics, determines the material dosage according to the soil conditions, avoids blind addition, and ensures the effective inhibition of soil microplastic migration. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram comparing the abundance of soil microplastics at a depth of 5 cm and 50 cm in Example 1 of the present invention;

[0034] Figure 2 Schematic diagram of the texture (clay and silt content) of shallow soil of different land use types in Example 1 of the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] A method for inhibiting the migration of microplastics in soil proposed by the present invention comprises the following steps:

[0038] Sampling soil at different depths to determine microplastic abundance and soil texture:

[0039] In this embodiment, 50 paired soil samples at a depth of 5 cm and 50 cm were collected on-site in a city in North China by a soil sampler. The samples covered 6 land types, including cultivated land, bare land, arbor woodland, grassland, shrub woodland, park and green space. The abundance of microplastics in soil samples was analyzed by laser direct infrared spectroscopy (LD IR) technology. In addition, the soil particle size classification method referred to the classification method of the International Soil Society, and the soil particles were divided into clay particles (<0.002 mm), silt particles (0.002-0.02 mm), and sand particles (>0.02 mm). The texture of the shallow soil was measured under wet conditions using a laser particle size analyzer (LS13320, Beckman Co., USA), and the abundance of soil microplastics at a depth of 5 cm and 50 cm and the texture of the shallow soil of different land types were obtained.

[0040] like Figure 1 As shown, the abundance of microplastics at 50 cm at all points was lower than that at 5 cm, of which 46% of the points had an abundance of microplastics at 50 cm that was more than 10% of that in the shallow soil, 50% of the points were between 1% and 10%, and 4% of the points had an abundance of microplastics at 50 cm that was less than 1% of that in the shallow soil; while in the present invention, [MP] 深层 / [MP] 浅层 The threshold of 10% covers 46% and 54% of the samples respectively, which is reasonable and can represent the difference ratio of microplastic abundance in deep and shallow layers in real soil;

[0041] like Figure 2 As shown in the figure, the mean values ​​of clay and silt content in soil of different land use types are all around 30%, so it is reasonable to select 30% as the judgment threshold.

[0042] Determine the formula and dosage of soil conditioner according to soil characteristics and prepare soil conditioner:

[0043] In this embodiment, 180 mesh hematite and gibbsite were used as raw materials, the ball milling speed was 300 rpm, the ball milling time was 1 hour, the soil conditioner was added to the soil at a specific depth and water was added to make the soil reach 60% of the saturated moisture content, and the soil was cured for 5 days;

[0044] Typical soil was selected from the above soil samples as experimental soil, and the soil microplastic stabilization effect was evaluated through soil leaching experiments to obtain the soil microplastic stabilization rate, including the following steps:

[0045] 10 g (by dry weight) of soil before adding materials and after adding materials and curing were placed in a Buchner funnel, and a stainless steel filter membrane with a pore size of 10 μm was placed at the bottom;

[0046] Use 1L of ultrapure water to leach the soil, collect the leachate, analyze the abundance of microplastics in the leachate, compare the abundance with the abundance of the original soil leachate, and obtain the stabilization rate η, the formula is as follows:

[0047]

[0048] Soil 1: Soil clay + silt content is 25.4%, and [MP] 深层 / [MP] 浅层 The stabilization rate of soil microplastics obtained by adding different amounts of soil conditioners is shown in Table 1 below.

[0049]

[0050] Table 1: Stabilization rate of soil microplastics obtained by adding different amounts of soil conditioners to soil 1

[0051] As shown in Table 1, when the dosage is 0.5, the stabilization rate is only 35%. It can be concluded that due to the low dosage of soil conditioner, the stabilization effect of hematite on soil microplastics is not good, and the adsorption and stabilization effect of hematite on microplastics cannot be fully exerted;

[0052] When the dosage is 1, the stabilization rate reaches 82%. At this dosage, hematite begins to play a better role and can effectively adsorb negatively charged soil microplastics, thereby improving the stabilization degree of soil microplastics; when the dosage is 5, the stabilization rate is 96%, which is further improved compared to the dosage of 1. This shows that with the increase of hematite dosage, its stabilization effect on soil microplastics is also enhanced.

[0053] When the dosage is 7, the stabilization rate is 98%. Although the stabilization rate is higher than that when the dosage is 5, since the dosage has exceeded the appropriate range (1-5g) at this time, it can be concluded that increasing the dosage within a certain range can improve the stabilization effect, but exceeding the appropriate range will not bring significant improvement in the effect.

[0054] Example 2

[0055] The difference between this embodiment and embodiment 1 is that the clay + silt content of the experimental soil, [MP] 深层 / [MP] 浅层 different.

[0056] Soil 2: Soil clay + silt content is 26.6%, [MP] 深层 / [MP] 浅层The stabilization rate of soil microplastics obtained by adding different amounts of soil conditioners is shown in Table 2 below:

[0057]

[0058] Table 2: Stabilization rate of soil microplastics obtained by adding different amounts of soil conditioners to soil 2

[0059] As shown in Table 2, when the dosage is 1, the stabilization rate is 47%. It can be concluded that due to the low dosage of the soil conditioner, the stabilization effect of hematite on soil microplastics is not good at this dosage, and the migration of soil microplastics cannot be effectively inhibited; when the dosage is 3, the stabilization rate is 58%. It can be concluded that the effect of hematite at this dosage is enhanced, but it is not enough to achieve a good stabilization effect.

[0060] When the dosage was 5, the stabilization rate was 79%, which was significantly improved compared with the dosage of 3, indicating that with the increase of hematite dosage, its stabilization effect on soil microplastics was significantly enhanced; when the dosage was 10, the stabilization rate was 97%, and the stabilization rate was further improved, indicating that at this dosage, hematite had a significant stabilization effect on soil microplastics, achieving the goal of improving the stabilization rate of soil microplastics;

[0061] Example 3

[0062] The difference between this embodiment and embodiments 1 and 2 is that the clay + silt content of the experimental soil, [MP] 深层 / [MP] 浅层 different.

[0063] Soil 3: Soil clay + silt content is 49.0%, [MP] 深层 / [MP] 浅层 The content of microplastics in soil is 5.5%, 70-90% hematite + 10-30% gibbsite is selected as the formula, 1-5g soil conditioner is added to 100g soil, and the stabilization rate of soil microplastics obtained by adding different amounts of soil conditioner is shown in Table 3 below:

[0064]

[0065] Table 3: The stabilization rate of soil microplastics obtained by adding different amounts of soil conditioners to soil 3 is shown in Table 3. When the soil conditioner formula is only hematite:

[0066] When the dosage is 1, the stabilization rate is 48%, and when the dosage is 5, the stabilization rate is 62%. It can be concluded that for soil 3, when only hematite is used, even if the dosage is increased, the stabilization rate is low and the stabilization effect is poor.

[0067] When the soil conditioner formula is 80% hematite + 20% gibbsite:

[0068] When the dosage is 0.5, the stabilization rate is 56%. It can be concluded that although gibbsite is introduced at this dosage, the dosage is insufficient and the stabilization effect is not good.

[0069] When the dosage is 1, the stabilization rate is 83%, which is higher than that when the dosage is 0.5. It can be concluded that after the introduction of gibbsite and the increase of the dosage, the stabilization effect is enhanced. Since gibbsite has a stronger positive charge, it can better adsorb negatively charged soil microplastics and synergize with hematite to improve the stabilization ability of soil microplastics.

[0070] When the dosage is 5, the stabilization rate is 95%, and the stabilization effect is further improved. It can be concluded that the combination of hematite and gibbsite can effectively inhibit the migration of soil microplastics;

[0071] When the soil conditioner formula is 90% hematite + 10% gibbsite:

[0072] When the dosage is 1, the stabilization rate is 77%. It can be concluded that the soil conditioner with a formula of 90% hematite + 10% gibbsite can also achieve a good stabilization effect. Although the stabilization rate is slightly lower than that of the soil conditioner with a formula of 80% hematite + 20% gibbsite, it can still meet the requirements.

[0073] When the soil conditioner formula is 95% hematite + 5% gibbsite:

[0074] When the dosage is 1, the stabilization rate is 56%, which shows that the stabilization effect is poor due to the low proportion of gibbsite.

[0075] Example 4

[0076] The difference between this embodiment and embodiments 1, 2, and 3 is that the clay + silt content of the experimental soil, [MP] 深层 / [MP] 浅层 different.

[0077] Soil 4: Soil clay + silt content is 47.9%, [MP] 深层 / [MP] 浅层 The stabilization rate of soil microplastics obtained by adding different amounts of soil conditioners is shown in Table 4 below:

[0078]

[0079]

[0080] Table 4: The stabilization rate of soil microplastics obtained by adding different amounts of soil conditioners to soil 4 is shown in Table 4. When the soil conditioner formula is only hematite:

[0081] When the dosage is 5, the stabilization rate is 36%; when the dosage is 10, the stabilization rate is 51%. It can be concluded that for soil 4, when the soil conditioner formula only uses hematite, the stabilization effect is poor, and even if the dosage is increased, a better stabilization level cannot be achieved.

[0082] When the soil conditioner formula is 80% hematite + 20% gibbsite:

[0083] When the dosage is 4, the stabilization rate is 60%, which is a certain improvement compared to when only hematite is used. However, due to the insufficient dosage, the stabilization effect is not good.

[0084] When the dosage was 5, the stabilization rate was 86%, indicating that the stabilization effect was enhanced after increasing the dosage, and the combination of hematite and gibbsite could play a role and effectively inhibit the migration of soil microplastics;

[0085] When the dosage is 10, the stabilization rate is 92%, and the stabilization effect is further improved. It can be concluded that increasing the dosage can further improve the stabilization ability of soil microplastics.

[0086] When the soil conditioner formula is 90% hematite + 10% gibbsite:

[0087] When the dosage is 5, the stabilization rate is 75%. It can be concluded that the soil conditioner with a formula of 90% hematite + 10% gibbsite can also achieve a good stabilization effect. Although the stabilization rate is slightly lower than that of the soil conditioner with a formula of 80% hematite + 20% gibbsite, it can still meet the requirements.

[0088] When the soil conditioner formula is 95% hematite + 5% gibbsite:

[0089] When the dosage is 5, the stabilization rate is 52%. It can be concluded that the stabilization effect is not good due to the low proportion of gibbsite in this formula.

[0090] The present invention determines different soil characteristics through sampling and analysis, adopts soil conditioners with different formulas and dosages to specifically inhibit the migration of soil microplastics, and uses hematite and gibbsite as raw materials, utilizes electrostatic attraction to stabilize microplastics, and gibbsite as auxiliary reinforcement to avoid unnecessary addition to weakly mobile soils, saving costs and resources. The present invention constructs an original microplastic stabilization effect evaluation method, which provides reliable standards and scientific basis for evaluating and optimizing the inhibition of soil microplastic migration, and improves the efficiency and quality of governance. In addition, the present invention first quantitatively analyzes the abundance of soil microplastics, determines the material dosage according to the soil conditions, avoids blind addition, and ensures the effective inhibition of soil microplastic migration.

[0091] The above specific embodiments are only several optional embodiments of the present invention. Based on the technical solutions of the present invention and the relevant inspirations of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A method for inhibiting the migration of soil microplastics, characterized in that: The following steps are involved: Sampling soil at different depths and determining microplastic abundance and soil texture; Determine the formula and dosage of soil conditioner according to soil characteristics and prepare soil conditioner; The soil conditioner is added to the soil at a specific depth and water is added to adjust the soil moisture content, and the treated soil is maintained; The stabilization effect of soil microplastics was evaluated through soil leaching experiments, and the stabilization rate of soil microplastics was obtained.

2. A method for inhibiting soil microplastic migration according to claim 1, characterized in that: The method of sampling soil at different depths and determining the abundance of microplastics and soil texture comprises the following steps: The shallow soil at a depth of 0-10 cm and the deep soil at a depth of 40-60 cm were sampled by a soil sampler; Microplastic characterization techniques, including infrared spectroscopy and laser confocal microscopy, were used to obtain the abundance of soil microplastics at two depths, recorded as [MP] 浅层 , [MP] 深层 ; The ratio of the abundance of microplastics in deep and shallow soil is calculated as [MP] 深层 / [MP] 浅层 , and at the same time analyze the soil texture at a depth of 0-10cm to obtain the clay + silt content.

3. A method for inhibiting soil microplastic migration according to claim 1, characterized in that: The formula and dosage determination method of the soil conditioner include: Soil clay + silt content ≤ 30% and [MP] 深层 / [MP] 浅层 ≤10%, choose only hematite as the formula, add 1-5g soil conditioner to 100g soil; Soil clay + silt content ≤ 30% and [MP] 深层 / [MP] 浅层 >10%, choose only hematite as the formula, add 5-10g soil conditioner to 100g soil; Soil clay + silt content> 30% and [MP] 深层 / [MP] 浅层 ≤10%, select 70-90% hematite + 10-30% gibbsite as the formula, add 1-5g soil conditioner to 100g soil; Soil clay + silt content> 30% and [MP] 深层 / [MP] 浅层 >10%, select 70-90% hematite + 10-30% gibbsite as the formula, and add 5-10g soil conditioner to 100g soil.

4. A method for inhibiting soil microplastic migration according to claim 3, characterized in that: The preparation method of the soil conditioner comprises selecting 150-200 mesh hematite and 150-200 mesh gibbsite as raw materials, and mixing the two according to a determined formula ratio.

5. A method for inhibiting soil microplastic migration according to claim 3, characterized in that: The mixing is performed by ball milling, the ball milling speed is 200-300 rpm, and the ball milling time is 1-2 hours.

6. A method for inhibiting soil microplastic migration according to claim 1, characterized in that: After adding the prepared soil conditioner to the soil at a depth of 0-20 cm, water is added to make the soil reach a saturated moisture content of 50-70%, and the treated soil is maintained for 3-7 days.

7. A method for inhibiting soil microplastic migration according to claim 1, characterized in that: The soil leaching experiment comprises the following steps: Take 8-12g of soil before adding materials and after adding materials and curing, respectively, and place them in a Buchner funnel, with a filter membrane placed at the bottom; Use 0.5-1.5L ultrapure water to leach the soil, collect the leachate, analyze the abundance c of microplastics in the leachate, compare the abundance with the abundance c0 of the original soil leachate, and obtain the stabilization rate η, the formula is as follows:

8. A method for inhibiting soil microplastic migration according to claim 7, characterized in that: The filter membrane is a stainless steel filter membrane with a pore size of 5-20 μm.

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