Ecological interception system for treating non-point source micro-plastic pollution by utilizing plant rhizosphere effect and construction method

Abstract

The invention discloses an ecological interception system for treating non-point source micro-plastic pollution by utilizing a plant rhizosphere effect and a construction method. The ecological interception system comprises an improved matrix and a plant buffer zone planted on the matrix, a weak acid organic adsorption layer and the plant buffer zone are formed through the improved red soil matrix to intercept the micro-plastics, and iron-rich acid red soil in the improved matrix can effectively adsorb the micro-plastics and prevent infiltration. A three-dimensional (3D) network structure is formed by growth of fibrous root type and straight root type plants with different growth characteristics on the ground and root systems of the plants, formation of a biological membrane is enhanced by root exudates of the plants, a water-permeable biological filter layer is constructed, migration and infiltration of non-point source micro-plastics are effectively intercepted, the interception efficiency of micro-plastics with the micron-grade particle size reaches 80% or above, and the interception effect is good. Microplastic pollution of downstream water is reduced, and drinking safety of underground water is guaranteed. The ecological interception system has great theoretical significance and application value in prevention and control of non-point source micro-plastic pollution, guarantee of river and lake water quality and drinking safety of underground water.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental pollution remediation, and more specifically, relates to an ecological interception system and a construction method for treating non-point source microplastic pollution by utilizing plant rhizosphere effect. Background Art

[0002] The concept of microplastics was first proposed by Thompson and others to refer to plastic particles with a particle size of less than 5mm that are decomposed from plastics. At present, microplastics have been found in various connected organs and tissues of the human body. ① Blood: In 2020, scientists detected microplastic pollution in human blood for the first time, and found such tiny particles in nearly 80% of the samples of experimental subjects. ② Lungs: In 2021, a research team from the University of Hull in the UK discovered microplastics deep in the lungs of living people for the first time. Microplastics with diameters ranging from 4μm to 2mm appeared in the lung tissues of 11 people in 3 research samples. Among them, the narrow lower half of the lungs had the largest number and the largest volume of particles. ③ Liver: The University of Hamburg in Germany found that microplastics were also present in the liver tissues of some patients with cirrhosis. ④ Feces: Scientists have also found evidence of the existence of microplastics in human feces, and it is particularly serious in patients with inflammatory bowel disease. The study also found that the content of microplastics in children's feces is higher than that in adults. ⑤ Placenta: Italian scientists detected microplastics in the placenta for the first time in 2020. Among the six human placental specimens, four human placental cell samples contained microplastic fragments. Microplastic particles invading the human body will inevitably destroy the human immune system and have an irreversible and profound impact on human life and reproduction.

[0003] Microplastics can spread around the world through the atmosphere, water bodies, etc., and continue to accumulate in the environment. Microplastics are now present in drinking water, wastewater, seawater and other aquatic environments. Due to their small size, difficulty in degradation and toxicity, they are easily ingested by zooplankton, fish and other organisms in the aquatic environment, causing necrosis of biological organs or even death. Additives are added during the processing and production of plastics, and when microplastics degrade in the aquatic environment, the additives are gradually released. In addition, microplastics with a large specific surface area have a certain adsorption capacity for organic pollutants such as organochlorine pesticides, polycyclic aromatic hydrocarbons and polychlorinated biphenyls, which have a negative impact on aquatic organisms. There are a large number of fiber microplastics in the atmospheric environment, most of which come from synthetic textiles. In rainy weather, microplastics in the atmosphere will be washed into rivers, lakes and seas by rainwater, thereby endangering the ecological environment and human health. Microplastics were found in all sampling points arranged by the atmospheric environment monitoring center. Studies have shown that surface dust and dust are the main sources of microplastics in the atmospheric environment. Land microplastics are mainly produced by human activities, mainly from point source pollution and non-point source pollution. Point source pollution includes sewage treatment and sewage sludge application, primary microplastics entering industrial wastewater and domestic sewage, and synthetic microfibers in laundry wastewater, which enter the soil ecosystem through sewage discharge, wastewater irrigation and sludge application. In agriculture, wastewater irrigation of plants is one of the main ways for microplastics to enter farmland ecosystems. In life, synthetic microfibers produced during laundry and tumble dryers are one of the sources of microplastics in farmland ecosystems. Non-point pollution sources refer to various environmental pollution without fixed pollution sources in a broad sense, and mainly refer to non-point source pollution of water environment in a narrow sense. The pollution sources of non-point pollution sources in a narrow sense mainly include urban surface runoff, fertilizer and pesticide use, rural domestic wastewater and solid waste, soil erosion and decentralized livestock and poultry farming. Pesticides and fertilizers are the main components of non-point pollution sources. The widespread use of mulch in agriculture has become one of the sources of secondary plastic particles in farmland ecosystems. Particles and microfibers produced by landfills or other surface sediments can be carried by air and enter terrestrial ecosystems through atmospheric deposition.

[0004] At present, research on the control of microplastic pollution includes the use of adsorption materials and potential microbial degradation, but it mainly focuses on indoor research and point source control. The sources of non-point source pollution are complex and the paths are uncertain. Plant buffer zones are recognized as an effective measure for the prevention and control of non-point source pollution. At present, the plant buffer zone technology for nitrogen and phosphorus control is mature. The mechanism of nitrogen and phosphorus removal is plant absorption, biodegradation, and matrix adsorption. However, the characteristics of microplastics are completely different. Their properties are stable but their types are diverse. They are difficult to absorb and biodegrade by plants. The adsorption effect of ordinary soil is low. The removal of microplastics is more considered by physical interception, but general filter cloths themselves have the risk of carrying microplastics, and the pore size is too small to be conducive to water infiltration, and the pore size is too large to be conducive to intercepting microplastics. At present, there is still a lack of technical solutions for the ecological interception of non-point source microplastic pollution. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects and shortcomings in the prior art and to provide an ecological interception system for treating non-point source microplastic pollution by utilizing the plant rhizosphere effect.

[0006] The second object of the present invention is to provide a method for constructing the ecological interception system.

[0007] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0008] The present invention first provides an ecological interception system for treating non-point source microplastic pollution by using plant rhizosphere effect, including a matrix and a plant buffer zone planted on the matrix; the matrix is ​​divided into three layers, the bottom layer is paved with gravel with a particle size of 1 to 2 cm, the middle layer is paved with organic matter-improved weakly acidic red soil, and the surface layer is paved with gravel with a particle size of 2 to 3 cm; the organic matter-improved weakly acidic red soil contains more than 3% organic matter, a pH of 5.5 to 6.5, and free Fe in fine soil. 2 O 3 >2%; the plant buffer zone includes an edge zone and a core zone, the edge zone is located outside the core zone, and is planted with low plants with fibrous roots whose height is less than 0.5m; the core zone is located in the central area of ​​the plant buffer zone, and is planted with tall plants with taproots whose height is greater than 0.8m; a biofilm is formed in the plant root area of ​​the plant buffer zone; a water inlet is provided on the surface layer at one end of the substrate, and a water outlet is provided on the surface layer and the bottom layer at the other end of the substrate.

[0009] The ecological interception system constructed by the present invention is designed mainly from the following three aspects: (1) different levels of matrix matching, from the surface to the bottom layer: large gravel, improved soil, small gravel. The improved soil adopts red soil improved by organic matter. The red soil is weakly acidic, rich in Fe, and has strong adsorption capacity. It also enhances the electrochemical activity of microorganisms and their degradation of microplastics, effectively adsorbs microplastics and prevents infiltration; (2) Plant combination: by effectively matching plants with different root characteristics and richness, the formation of an above-ground "small forest" and an underground "ecological network" is achieved, forming a hilly three-dimensional distribution of above-ground vegetation and underground roots; (3) Biofilm cultivation: wetland plant litter is used to improve soil organic matter, which increases soil fertility while also increasing the formation of biofilm. Area and thickness; the mechanism by which the constructed plant buffer zone exerts its interception efficiency is: the effective combination of plants with different root characteristics can form a dense and strong mesh structure at the root interface, fibrous root plants are mainly distributed horizontally, taproot plants are mainly distributed vertically, and reasonable combination of plants forms a three-dimensional 3D network structure, the first interception effect: use adsorption to directly intercept plastic particles and large-particle microplastics in surface runoff, the second interception effect: root secretions enhance the colonization of microorganisms on the mesh structure and form a biofilm with finer pores. The viscosity of the biofilm can effectively adhere to small-particle microplastics, the third interception effect: the vertically layered biofilm can be used as a filter with different pore sizes to reduce the sinking of microplastic particles.

[0010] Furthermore, the substrate bottom layer is laid with a thickness of 8 to 12 cm, the substrate middle layer is laid with a thickness of 23 to 37 cm, and the substrate surface layer is laid with a thickness of 3 to 7 cm.

[0011] Preferably, the substrate bottom layer is laid with a thickness of 10 cm, the substrate middle layer is laid with a thickness of 35 cm, and the substrate surface layer is laid with a thickness of 5 cm.

[0012] Furthermore, the preparation method of the organic matter improved weakly acidic red soil is to keep the wetland plant litter fragments moist at 30-35°C with domestic sewage in a weight ratio of 1:1, and when mucus appears on the surface, mix them with red soil in a weight ratio of 3:1 to obtain the organic matter improved weakly acidic red soil.

[0013] Preferably, the wetland plant litter fragments are kept moist with domestic sewage for three weeks.

[0014] Preferably, the red soil is selected from the red soil in South China. The red soil in South China is rich in iron and has stronger adsorption capacity.

[0015] Furthermore, the number of plant species in the plant buffer zone is 2 to 6, that is, at least one fibrous root type short plant and one taproot type tall plant are planted.

[0016] Preferably, the number of plant species planted is 2 to 4.

[0017] Further preferably, the number of plant species planted is 4.

[0018] Furthermore, the plants in the plant buffer zone are wetland plants.

[0019] Preferably, plant species are selected based on field surveys and availability of germplasm resources, and the criteria are large biomass, strong growth adaptability, long growth cycle, and strong root system.

[0020] Furthermore, the taproot type plants have obvious taproots, which extend vertically downward and grow lateral roots at a certain distance. The root neck is relatively narrow and protruding, and the plants are upright, which is suitable for mowing. The fibrous root type plants are composed of many adventitious roots of similar thickness. The taproot cannot be clearly distinguished in the root system, which is suitable for consolidating soil and preventing loss. In terms of quantity, the taproot number of taproot plants and fibrous root plants is 1 and 0 respectively, the total number of roots is <30 and >100 respectively, and the root surface area density is <0.5 and >1.0m 2 / m 3 The root surface area density can reflect the degree of contact between the plant root system and the soil.

[0021] Preferably, the fibrous root type low plants are selected from one or more of Alternanthera philoxeroides, Macrophylla scabra, Licorice gracilis, and Chicory; the taproot type tall plants are selected from one or more of Windmill grass, Vetiver, Zea mays, and Phragmites australis.

[0022] Preferably, the fibrous root type short plants are selected from Alternanthera philoxeroides and Macrophylla sphaerocephala; the taproot type tall plants are selected from Pinus armandii and Vetiver odorifera.

[0023] Furthermore, the planting density of the fibrous root type low plants is 8 to 12 plants / m 2 The planting density of taproot tall plants is 3 to 4 plants / m 2 .

[0024] Furthermore, the planting ratio of the fibrous root type short plants to the taproot type tall plants is 2 to 2.5:1.

[0025] Preferably, the planting ratio of the fibrous root type short plants to the taproot type tall plants is 2:1.

[0026] Preferably, the plant buffer zone is planted with Alternanthera philoxeroides, Macrophylla oleifera, Pinus armandii and Vetiveria zizanioides, and the planting ratio thereof is 3:3:1.5:1.5.

[0027] Furthermore, the biofilm is formed by intermittently passing water to the plant buffer zone, with a COD load of 100 g / (m 2·d), each retention time is 1 to 2 hours. This method is a microbial culture method, a certain concentration of COD feeding, intermittent water inflow and a certain hydraulic retention time stimulate the formation of biofilm.

[0028] Preferably, by detecting that the release rate of TP, TSS, and Fe content in water is <10% to stable, and the COD removal rate reaches 70%, it indicates that the biofilm has grown mature and stable and can be used for microplastic interception.

[0029] Furthermore, the specific surface area, pore size and thickness of the membrane are 5 to 10 m 2 / g, 20~300nm, 0.1~2mm.

[0030] Preferably, the membrane specific surface area, pore size and thickness are 5 to 10 m 2 / g, 20~200nm, 0.5~1.2mm.

[0031] Preferably, the membrane specific surface area, pore size and thickness are 8 to 10 m 2 / g, 20~100nm, 0.8~1.2mm.

[0032] The present invention provides the application of the ecological interception system in the construction of an ecological buffer zone for controlling urban runoff pollution and / or non-point source pollution in villages and towns.

[0033] The present invention also provides a method for constructing any of the above-mentioned systems for ecological interception of non-point source microplastic pollution, comprising the following steps:

[0034] S1. Construction of planting matrix: gravel with a particle size of 1 to 2 cm is laid on the bottom layer, organic matter-improved weakly acidic red soil is laid on the middle layer, and gravel with a particle size of 2 to 3 cm is laid on the surface layer; the organic matter-improved weakly acidic red soil is prepared by keeping aquatic plant litter fragments moist with domestic sewage, and mixing with red soil at a weight ratio of 3:1 when mucus appears on the surface to form organic matter-improved weakly acidic red soil;

[0035] S2. Construction of plant buffer zone module: Plant low-growing plants with fibrous roots less than 0.5m in height around the plant buffer zone, and plant tall plants with taproots greater than 0.8m in height in the middle of the plant buffer zone;

[0036] S3. Form a biofilm in the plant root area in the plant buffer zone module.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention provides an ecological interception system for non-point source microplastic pollution using plant rhizosphere effect. The ecological interception system intercepts microplastics by improving the matrix and the plant buffer zone planted on the matrix. The acidic iron-rich red soil in the improvement mechanism can effectively adsorb microplastics and prevent infiltration. At the same time, the plant root growth and its biofilm formation characteristics are used to construct a permeable biological filtration layer to effectively intercept the migration and infiltration of non-point source microplastics. The interception efficiency reaches 80%, which reduces the microplastic pollution in downstream water bodies and the safety of groundwater drinking. The ecological interception system of the present invention has great theoretical significance and application value for the prevention and control of non-point source microplastic pollution and the protection of river and lake water quality and groundwater drinking safety: (1) Economic value: Based on the existing plant buffer zone, in-situ improvement is carried out, no additional land requisition is required, no additional engineering investment and infrastructure, and no high-precision and rare materials are involved. The main objects are common wetland plants, which are easy to obtain, easy to cultivate, easy to manage, and the harvest can be recycled. The overall engineering application investment and management cost are low, and maintenance is simple. (2) Ecological value: Using ecological principles to achieve harmless interception of microplastic pollution, with good surface interception and infiltration filtration effects, reducing the impact on surface river and lake water quality and reducing the risk of groundwater drinking. Different plant types and richness can form different habitats, which is conducive to biodiversity restoration and enhances the interception of non-point source pollution. (3) Social value: It forms an important part of the urban ecosystem that combines pollution purification and landscape greening, accumulates and purifies rainwater and surface runoff, helps solve the current prominent problems such as initial rainwater runoff pollution, urban waterlogging, and water shortage, and promotes harmonious coexistence between man and nature. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the ecological interception system for treating non-point source microplastic pollution using plant rhizosphere effect.

[0040] Figure 2 A diagram of a simulation device for testing the ecological interception technology of non-point source microplastic pollution; wherein: 1-water tank and pump, 2-plant planting module, 3-load-bearing base, 4-water tank, 5-sprinkler, 21-plant-free module, 22-low-richness plant module, 23-medium-richness plant module, 24-high-richness plant module, 25-water inlet, 26-sampling port. DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0042] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0043] Example 1

[0044] like Figure 1 As shown, this embodiment provides an ecological interception system for treating non-point source microplastic pollution by using plant rhizosphere effect, including a matrix and a plant buffer zone planted on the matrix; the matrix is ​​divided into three layers, the bottom layer is paved with gravel with a particle size of 1 to 2 cm, the middle layer is paved with organic matter-improved weakly acidic red soil, and the surface layer is paved with gravel with a particle size of 2 to 3 cm; the organic matter-improved weakly acidic red soil contains organic matter>3%, pH 5.5 to 6.5, and free Fe in fine soil 2 O 3 >2%; the plant buffer zone includes an edge zone and a core zone, the edge zone is located outside the core zone, and is planted with low plants with fibrous roots whose height is less than 0.5m; the core zone is located in the central area of ​​the plant buffer zone, and is planted with tall plants with taproots whose height is greater than 0.8m; a biofilm is formed in the plant root area of ​​the plant buffer zone; a water inlet is provided on the surface layer at one end of the substrate, and a water outlet is provided on the surface layer and the bottom layer at the other end of the substrate.

[0045] This embodiment also provides a method for constructing the above ecosystem, comprising the following steps:

[0046] S1. Construction of planting matrix: a 10 cm thick layer of small-grained gravel with a particle size of 1 to 2 cm is laid on the bottom layer, a 35 cm thick layer of organic matter-improved weakly acidic red soil is laid in the middle layer, and a 5 cm thick layer of large-grained gravel with a particle size of 2 to 3 cm is laid on the top layer; the organic matter-improved weakly acidic red soil is prepared by keeping aquatic plant litter fragments moist at 30 to 35°C with domestic sewage at a weight ratio of 1:1, and mixing with red soil when mucus appears on the surface to form an improved soil planting layer; the red soil is selected from the red soil in South China.

[0047] S2. Construction of plant buffer zone module: Plant low-growing plants with fibrous roots less than 0.5m in height around the plant buffer zone, with a planting density of 8 to 12 plants / m 2 ; Taproot tall plants with a height greater than 0.8m are planted in the middle of the plant buffer zone, with a planting density of 3 to 4 plants / m 2 .

[0048] S3. Two weeks after the plants were planted, artificial water was introduced intermittently twice a week, with a COD load of 100 g / (m 2 d), the residence time was 1 to 2 hours, the budding of plants above the ground was observed, a small amount of soil from the plant rhizosphere interface was collected, and the release rate of TP, TSS, and Fe in the water was detected to be <10% to stable, and the COD removal rate reached 70%, indicating that the biofilm grew mature and stable. At the same time, the specific surface area, pore size, and thickness of the biofilm were detected to be 5 to 10 m 2 / g, 20-300nm, 0.1-2mm, you can start intercepting microplastics.

[0049] Among them, the plants in step S2 are wetland plants, and the plant species are selected according to field investigations and the availability of germplasm resources. The evaluation criteria are large biomass, strong growth adaptability, long growth cycle, and strong roots. Among them, at least one fibrous-rooted low-growing plant and one taprooted tall-growing plant are planted; the fibrous-rooted low-growing plants are selected from one or more of Alternanthera philoxeroides, Axonopus compressus, Scoparia dulcis, and Sonchus oleraceus; the taprooted tall-growing plants are selected from one or more of Cyperus involucratus, Vetiveria zizanioides, Thalia dealbata, and Phragmites australis.

[0050] Furthermore, the existing plant buffer zone can be in-situ improved according to the above method to achieve the interception effect of non-point source microplastic pollution.

[0051] Example 2

[0052] This example provides a method for constructing an ecological interception system for treating non-point source microplastic pollution by using the rhizosphere effect of plants, including the following steps:

[0053] S1. Construction of the planting substrate: A 2-cm-diameter small gravel layer with a thickness of 8 cm is laid at the bottom layer, a 35-cm-thick organic matter-improved weakly acidic red soil layer is laid in the middle layer, and a 3-cm-diameter large gravel layer with a thickness of 3 cm is laid at the top layer; the organic matter-improved weakly acidic red soil is formed by mixing aquatic plant litter fragments with red soil at 30-35 °C and keeping them moist with domestic sewage at a weight ratio of 1:1 until mucus appears on the surface; the red soil is selected from the red soil in South China.

[0054] S2. Construction of the plant buffer zone module: Fibrous-rooted low-growing plants with a plant height less than 0.5 m are planted around the plant buffer zone at a planting density of 8 plants / m 2 ; Taprooted tall-growing plants with a plant height greater than 0.8 m are planted in the middle of the plant buffer zone at a planting density of 3 plants / m 2 .

[0055] S3. Two weeks after the plants are planted, start intermittent artificial water inflow twice a week, with a COD load of 100 g / (m 2 ·d), a retention time of 2 hours, observe the budding situation above the ground of the plants, collect a small amount of soil at the rhizosphere interface of the plants, and detect that the release rates of TP, TSS, and Fe in the effluent water reach <10% and are stable, and the COD removal rate reaches 70%, indicating that the biofilm grows mature and stable. At the same time, detect that the specific surface area, pore size, and thickness of the biofilm reach 5-10 m 2 / g, 20-300 nm, and 0.1-2 mm respectively, then microplastic interception can be started.

[0056] Among them, at least one fibrous-rooted low-growing plant and one taprooted tall-growing plant are planted in the plant buffer zone; the fibrous-rooted low-growing plant is selected from one of Alternanthera philoxeroides, Axonopus compressus, Scoparia dulcis, Sonchus oleraceus; the taprooted tall-growing plant is selected from one of Cyperus involucratus, Vetiveria zizanioides, Thalia dealbata, Phragmites australis.

[0057] Example 3

[0058] This example provides a construction method for an ecological interception system for treating non-point source microplastic pollution using the rhizosphere effect of plants, including the following steps:

[0059] S1. Construction of the planting substrate: A 12-cm-thick layer of small gravel with a particle size of 1 cm is laid at the bottom layer, a 35-cm-thick layer of organic matter-improved weakly acidic red soil is laid in the middle layer, and a 7-cm-thick layer of large gravel with a particle size of 2 cm is laid on the top layer; the organic matter-improved weakly acidic red soil is formed by mixing aquatic plant litter fragments with red soil at a weight ratio of 1:1 of domestic sewage and keeping it moist at 30-35 °C until mucus appears on its surface to form an improved soil planting layer; the red soil is selected from the red soil in South China.

[0060] S2. Construction of the plant buffer zone module: Fibrous-rooted low-growing plants with a plant height less than 0.5 m are planted around the plant buffer zone, and the planting density is 12 plants / m 2 ; Taprooted tall-growing plants with a plant height greater than 0.8 m are planted in the middle of the plant buffer zone, and the planting density is 4 plants / m 2 .

[0061] S3. Two weeks after the plants are planted, start intermittent inflow of artificial wastewater twice a week, with a COD load of 100 g / (m 2 ·d), a residence time of 1 hour, observe the budding situation of the plants above the ground, collect a small amount of soil at the rhizosphere interface of the plants, and detect that the release rates of TP, TSS, and Fe in the effluent water reach <10% and are stable, and the COD removal rate reaches 70%, indicating that the biofilm grows mature and stable. At the same time, detect that the specific surface area, pore size, and thickness of the biofilm reach 5-10 m 2 / g, 20-300 nm, 0.1-2 mm respectively, then microplastic interception can be started.

[0062] Among them, at least one fibrous-rooted low-growing plant and one taprooted tall-growing plant are planted in the plant buffer zone, and the fibrous-rooted low-growing plant is selected from one or more of Alternanthera philoxeroides, Axonopus compressus, Scoparia dulcis, Sonchus oleraceus; the taprooted tall-growing plant is selected from one or more of Cyperus involucratus, Vetiveria zizanioides, Thalia dealbata, Phragmites australis.

[0063] Test example

[0064] According to the ecological interception system for treating non-point source microplastic pollution using the rhizosphere effect of plants and its construction method in Example 1, design as Figure 2 The simulation device shown compares the effect of removing microplastics from the inlet and outlet water of plant modules with different species richness. The device includes a water tank and pump 1, a plant planting module 2, a load-bearing base 3, a water tank 4, and a nozzle 5. The plant planting module 2 is divided into a mutually independent plant-free module 21, a low-richness plant module 22, a medium-richness plant module 23, and a high-abundance plant module 24; the plant-free module 21, the low-richness plant module 22, the medium-richness plant module 23, and the high-abundance plant module 24 are all provided with a water inlet 25 on the upper layer at the left end, and a sampling port 26 on the bottom layer; the plant planting modules with different richness contain a matrix and plants planted on the matrix; preferably, the right end surface layer of the plant planting module 2 is also provided with a water outlet.

[0065] The specific method for setting up the simulation device and comparing the effect of removing microplastics from the inlet and outlet water of plant modules with different species richness is as follows:

[0066] (1) Design of water inlet and outlet: Each plant planting module with different richness in the square plant planting module is provided with a water inlet and a sampling port, that is, a water inlet is provided on the left end of the substrate surface of each plant planting module with different richness, which serves as the water inlet of the experimental water (actual domestic sewage and surface runoff), and a sampling port is provided on the right end of the substrate bottom layer, which serves as the collection port for the infiltration runoff water, with a diameter of 3 cm; further, a water outlet is also provided on the right end of the substrate surface of the plant planting module as the surface runoff water.

[0067] (2) Substrate modification and composition: 10 cm of fine gravel (1 cm in diameter) at the bottom, 35 cm of organic matter-improved weakly acidic red soil in the middle layer, and aquatic plant litter fragments at a weight ratio of 1:1 kept moist with domestic sewage at 35°C for three weeks. When mucus appears on the surface, it can be mixed with the red soil to form an improved soil planting layer. A 5 cm layer of coarse gravel (2 cm in diameter) is laid on the top layer. The red soil is selected from the red soil in South China.

[0068] (3) Construction of plant planting modules: Construct different types of plant buffer zone modules, namely, no plant, low richness, medium richness, and high richness plant modules, with 0, 2, 4, and 8 species, respectively. Plant planting order: fibrous root-type short plants (plant height <0.5 m) are planted around the front and back (8-12 plants / m 2 ), taproot tall plants (plant height>0.8m) are planted in the middle (planting density 3-4 plants / m 2 ), forming a hilly three-dimensional distribution of above-ground vegetation and underground root systems.

[0069] (4) Operation time: Two weeks after the plants were planted, intermittent artificial water supply was started twice a week, and the COD load was 100g / (m 2·d), the residence time is 1 to 2 hours, observe the above-ground budding of plants, collect a small amount of soil from the plant rhizosphere interface, and test the specific surface area, pore size, and thickness of the biofilm, which are 5 to 10 m 2 / g, 20-300nm, 0.1-1mm, and the release rate of TP, TSS, and Fe in the water is detected to be <10% to stable, and the microplastic interception test can be started when the COD removal rate reaches 70%. The interception test influent is actual domestic sewage and surface runoff.

[0070] (5) Detection indicators: Detect the content of microplastics in the runoff from the surface and bottom outlets of each module to evaluate the surface interception and infiltration effects of the plant buffer zone as a whole; detect the content of microplastics in the soil of the vertical layers of the plant planting area, including the surface layer (0-10 cm), middle layer (10-20 cm) and bottom layer (20-30 cm), to evaluate the interception effect of stems and leaves, root filtration effect, and soil fixation and infiltration effect of the plant buffer zone; detect the specific surface area, pore size and thickness of the rhizosphere biofilm to evaluate the maturity and filtration potential of the biofilm.

[0071] Result analysis:

[0072] The plant species and planting ratios in each plant module, as well as the technical parameters and interception effects of ecological interception of non-point source microplastic pollution are shown in Table 1. Compared with the high-richness (8 species) plant module, the low (2 species) and medium-richness (4 species) plant modules have low plant coverage, but the specific surface area and thickness of the rhizosphere biofilm formed by them are higher than those of the high-richness plant module, and the pore size is smaller; the low-richness and medium-richness plant modules have good interception effects on microplastics, which are 73.6% and 82.1% respectively. Among them, the medium-richness plant module has the best interception effect on microplastics, which also shows that the plant combination here is more suitable for PU material, with a concentration of 1g / L·m -2 The ecological interception effect of microplastic non-point source pollution.

[0073] Table 2 shows the differences in the vertical microplastic interception effects of different plants. Plants with different root characteristics intercepted 4 to 16 times more microplastics than modules without plants, reflecting the interception effect of plants. In addition, the outer fibrous root-type stoloniferous plants intercepted more microplastics than the inner main root erect stem-type plants (2240.83 vs 1141.06). The stratification pattern of microplastics in the matrix of modules without plants and modules with plants with different root characteristics was compared. The stratification pattern of the proportion of microplastics in the matrix of each module was middle layer (10-20 cm) > surface layer (0-10 cm) > bottom layer (20-30 cm). There was little difference between the surface and middle layers of the modules with fibrous root-type stoloniferous plants, which also reflected the influence of root characteristics. In addition, the content of microplastics in the bottom layer of the matrix in the plant module was less than that in the surface and middle layers, indicating that plants had a filtering effect on microplastics and effectively reduced the infiltration of microplastics.

[0074] Table 1 Structural parameters and interception effects of the ecological interception system for non-point source microplastic pollution

[0075]

[0076] Table 2 Plant configuration and layered interception effect of the ecological interception system for non-point source microplastic pollution

[0077]

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Claims

1. An ecological interception system for treating non-point source microplastic pollution using plant rhizosphere effect, characterized in that: It comprises a substrate and a plant buffer zone planted on the substrate; the substrate is divided into three layers, the bottom layer is paved with gravel with a particle size of 1-2 cm, the middle layer is paved with organic matter-improved weakly acidic red soil, and the surface layer is paved with gravel with a particle size of 2-3 cm; the organic matter in the organic matter-improved weakly acidic red soil is greater than 3%, the pH is 5.5-6.5, and the free Fe2O3 in the fine soil is greater than 2%; the plant buffer zone comprises an edge zone and a core zone, the edge zone is located outside the core zone, and is planted with fibrous root-type short plants with a plant height of less than 0.5 m; the core zone is located in the central area of ​​the plant buffer zone, and is planted with taproot-type tall plants with a plant height of more than 0.8 m; a biofilm is formed in the plant root area of ​​the plant buffer zone; a water inlet is provided on the surface layer at one end of the substrate, and a water outlet is provided on the surface layer and the bottom layer at the other end of the substrate.

2. The ecological interception system according to claim 1, characterized in that: The substrate bottom layer is laid with a thickness of 8 to 12 cm, the substrate middle layer is laid with a thickness of 23 to 37 cm, and the substrate surface layer is laid with a thickness of 3 to 7 cm.

3. The ecological interception system according to claim 1, characterized in that: The method for preparing the organic matter-improved weakly acidic red soil is as follows: wetland plant litter fragments are kept moist at 30-35° C. using domestic sewage at a weight ratio of 1:1, and when mucus appears on the surface, the fragments are mixed with red soil at a weight ratio of 1:3 to obtain the organic matter-improved weakly acidic red soil.

4. The ecological interception system according to claim 1, characterized in that: The plants in the plant buffer zone are wetland plants.

5. The ecological interception system according to claim 1, characterized in that: The number of plant species in the plant buffer zone is 2 to 6.

6. The ecological interception system according to claim 1, characterized in that: The fibrous root type low plants are selected from one or more of Alternanthera philoxeroides, Macrophylla scabra, Licorice gracilis, and Chicory; the taproot type tall plants are selected from one or more of Windmill grass, Vetiver, Zygophyllum, and Phragmites australis.

7. The ecological interception system according to claim 1, characterized in that: The planting density of the fibrous root type low plants is 8 to 12 plants / m 2 The planting density of taproot tall plants is 3 to 4 plants / m 2 .

8. The ecological interception system according to claim 1, characterized in that: The biofilm is formed by intermittently passing water to the plant buffer zone, with a COD load of 100 g / (m 2 ·d), each residence time is 1 to 2 hours. When the release rate of TP, TSS and Fe in the water is detected to be <10% to stable, and the COD removal rate reaches 70%, a mature and stable biofilm is obtained.

9. The ecological interception system according to claim 1, characterized in that: The specific surface area of ​​the biofilm is 5 to 10 m 2 / g, pore diameter is 20-300nm, and thickness is 0.1-2mm.

10. The method for constructing a system for ecological interception of non-point source microplastic pollution according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Construction of planting matrix: gravel with a particle size of 1 to 2 cm is laid on the bottom layer, organic matter-improved weakly acidic red soil is laid on the middle layer, and gravel with a particle size of 2 to 3 cm is laid on the surface layer; the organic matter-improved weakly acidic red soil is prepared by keeping aquatic plant litter fragments moist with domestic sewage, and mixing with red soil at a weight ratio of 1:3 when mucus appears on the surface to form organic matter-improved weakly acidic red soil; S2. Construction of plant buffer zone module: Plant low-growing plants with fibrous roots less than 0.5m in height around the plant buffer zone, and plant tall plants with taproots greater than 0.8m in height in the middle of the plant buffer zone; S3. Form a biofilm in the plant root area in the plant buffer zone module.

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